"Worthwhile" solutions have potential, but also limited impact and scalability. They might only be effective in some narrower, niche applications.

Increase Decentralized Composting

Image
Image
Peatland
Coming Soon
On
Description for Social and Search
Increase Decentralized Composting
Solution in Action
Speed of Action
left_text_column_width
Caveats
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Increase
Solution Title
Decentralized Composting
Classification
Worthwhile
Lawmakers and Policymakers
Practitioners
Business Leaders
Nonprofit Leaders
Investors
Philanthropists and International Aid Agencies
Thought Leaders
Technologists and Researchers
Communities, Households, and Individuals

Improve Aquaculture

Image
Image
An image of a boat next to an enclosed net used for aquaculture
Coming Soon
On
Summary

Improving aquaculture involves reducing CO₂ and other GHG emissions during the production of farmed fish and other aquatic animals through better feed efficiency and the decarbonization of on-farm energy use. Advantages include reduced demand for feedstocks produced from both wild capture fisheries and terrestrial sources, which benefits marine and terrestrial ecosystems. Disadvantages include the costs of transitioning to fossil-free energy sources. While these interventions are unlikely to lead to globally meaningful emissions reductions (>0.1 Gt CO₂‑eq/yr ), we consider Improve Aquaculture as “Worthwhile” given the rapid and ongoing expansion of the industry, its potential to replace higher-emission protein sources, and the ecosystem benefits of reducing feedstock demand.

Description for Social and Search
The Improve Aquaculture solution is coming soon.
Overview

What is our assessment?

While Improve Aquaculture is unlikely to have a major climate impact, our assessment concludes that it is “Worthwhile” due to its ability to reduce pressure on wild fish stocks and terrestrial biomass, and because efficiency improvements made now are likely to scale into greater climate impact as the sector continues to expand.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? No
Risk Is it risky or harmful? No
Cost Is it cheap? ?

What is it?

GHG emissions from aquaculture can be reduced by increasing the feed conversion efficiency of the cultured animals and decarbonizing on-farm energy use. Aquaculture – farming aquatic animals or plants for food or other purposes – is rapidly growing and now accounts for over half of the global production of aquatic animals, exceeding wild capture fisheries. Over 7% of human-consumed protein is aquaculture-produced. As this sector has grown, it has become increasingly reliant on external feed sources, with the share of non-fed aquaculture (e.g., bivalves that feed from the water column) dropping from nearly 40% in 2000 to 27% in 2022. Improving feed conversion ratios (FCR) – the amount of feed it takes to produce a given amount of biomass – can lower feed demand and reduce CO₂ and other GHG emissions tied to feed production and transport. FCRs can be improved by feed formulations that increase digestibility, genetic or breeding modifications to improve digestive efficiency in the cultured animal, species-specific feed formulations, and optimizing ration size and feeding frequency. At the same time, decarbonizing on-farm energy use can help reduce CO₂ emissions from common equipment, such as aerators and water pumps.

Does it work?

Interventions to improve feed and energy efficiency can reduce CO₂ emissions from aquaculture operations, although the potential achievable climate impact of these actions is currently unlikely to be globally meaningful (>0.1 Gt CO₂‑eq/yr ). Total annual emissions from aquaculture were estimated to be 0.26 Gt CO₂‑eq/yr in 2017, with nearly 60% of that attributed to feed production. Improving FCR is both plausible and effective, since it directly reduces the amount of food needed to cultivate fish and other species, thereby lowering emissions tied to feed production and transport. Between 1995 and 2007, improvements in FCR have ranged between 5 to 15% for a variety of species, including shrimp, salmon, carp, and tilapia.

Decarbonizing on-farm energy use can reduce equipment-related emissions, particularly in intensive systems that use energy for automated feeding systems, water temperature control, and circulation and aeration systems. In general, the potential impact of decarbonizing varies widely because on-farm energy use differs significantly across species and production systems. For instance, shrimp and prawn farming use nearly 20,000 MJ/t of live weight (LW), with over 75% from electricity, while bivalve production uses around 3,000 MJ/t of LW supplied largely by diesel.

Why are we excited?

Improving feed efficiency in aquaculture reduces demand for captured wild fish used in feed, reducing pressure on overfished stocks. It also lowers reliance on terrestrial biomass, such as soy, wheat, and rice, which come with additional land-use and emission costs. More efficient feeding can help reduce nutrient pollution, which can be responsible for high methane and nitrous oxide fluxes in some inland aquaculture systems. At the same time, decarbonizing on-farm energy use might ultimately lead to lower long-term operating costs and improved energy reliability.

Why are we concerned?

There are relatively few drawbacks associated with improving aquaculture. In the case of decarbonizing on-farm energy use, upfront costs could be high. For instance, installing solar panels or upgrading pumps can be financially challenging for small-scale operations. Energy use on farms can also vary throughout the day and night, which might not always align with renewable energy sources, like solar, without storage. 

Solution in Action

Badiola, M., Basurko, O. C., Piedrahita, R., Hundley, P., & Mendiola, D. (2018). Energy use in recirculating aquaculture systems (RAS): a review. Aquacultural Engineering, 81, 57-70. Link to source: https://doi.org/10.1016/j.aquaeng.2018.03.003

Boyd, C. E., McNevin, A. A., & Davis, R. P. (2022). The contribution of fisheries and aquaculture to the global protein supply. Food Security, 14(3), 805-827. Link to source: https://doi.org/10.1007/s12571-021-01246-9

Food and Agriculture Organization of the United Nations. (2018). The state of world fisheries and aquaculture. Food and Agriculture Organization of the United Nations. Link to source: https://openknowledge.fao.org/handle/20.500.14283/i9540en

Food and Agriculture Organization of the United Nations. (2024). The State of World Fisheries and Aquaculture 2024 – Blue Transformation in action. Food and Agriculture Organization of the United Nations. Link to source: https://openknowledge.fao.org/handle/20.500.14283/cd0683en

Henriksson, P. J. G., Troell, M., Banks, L. K., Belton, B., Beveridge, M. C. M., Klinger, D. H., ... & Tran, N. (2021). Interventions for improving the productivity and environmental performance of global aquaculture for future food security. One Earth, 4(9), 1220-1232. Link to source: https://doi.org/10.1016/j.oneear.2021.08.009

Jones, A. R., Alleway, H. K., McAfee, D., Reis-Santos, P., Theuerkauf, S. J., & Jones, R. C. (2022). Climate-friendly seafood: the potential for emissions reduction and carbon capture in marine aquaculture. BioScience, 72(2), 123-143. Link to source: https://doi.org/10.1093/biosci/biab126

MacLeod, M. J., Hasan, M. R., Robb, D. H., & Mamun-Ur-Rashid, M. (2020). Quantifying greenhouse gas emissions from global aquaculture. Scientific Reports, 10(1), 11679. Link to source: https://doi.org/10.1038/s41598-020-68231-8

Naylor, R. L., Hardy, R. W., Bureau, D. P., Chiu, A., Elliott, M., Farrell, A. P., ... & Nichols, P. D. (2009). Feeding aquaculture in an era of finite resources. Proceedings of the National Academy of Sciences106(36), 15103-15110. Link to source: https://doi.org/10.1073/pnas.0905235106

Naylor, R. L., Hardy, R. W., Buschmann, A. H., Bush, S. R., Cao, L., Klinger, D. H., ... & Troell, M. (2021). A 20-year retrospective review of global aquaculture. Nature, 591(7851), 551-563. Link to source: https://doi.org/10.1038/s41586-021-03308-6

Scroggins, R. E., Fry, J. P., Brown, M. T., Neff, R. A., Asche, F., Anderson, J. L., & Love, D. C. (2022). Renewable energy in fisheries and aquaculture: Case studies from the United States. Journal of Cleaner Production, 376, 134153. Link to source: https://doi.org/10.1016/j.jclepro.2022.134153

Shen, L., Wu, L., Wei, W., Yang, Y., MacLeod, M. J., Lin, J., ... & Zhuang, M. (2024). Marine aquaculture can deliver 40% lower carbon footprints than freshwater aquaculture based on feed, energy and biogeochemical cycles. Nature Food, 5(7), 615-624. Link to source: https://doi.org/10.1038/s43016-024-01004-y

Stentiford, G. D., Bateman, I. J., Hinchliffe, S. J., Bass, D. 1., Hartnell, R., Santos, E. M., ... & Tyler, C. R. (2020). Sustainable aquaculture through the One Health lens. Nature Food, 1(8), 468-474. Link to source: https://doi.org/10.1038/s43016-020-0127-5

Tacon, A. G., & Metian, M. (2008). Global overview on the use of fish meal and fish oil in industrially compounded aquafeeds: Trends and future prospects. Aquaculture, 285(1-4), 146-158. Link to source: https://doi.org/10.1016/j.aquaculture.2008.08.015

Vo, T. T. E., Ko, H., Huh, J. H., & Park, N. (2021). Overview of solar energy for aquaculture: The potential and future trends. Energies, 14(21), 6923. Link to source: https://doi.org/10.3390/en14216923

Zhang, Z., Liu, H., Jin, J., Zhu, X., Han, D., & Xie, S. (2024). Towards a low-carbon footprint: Current status and prospects for aquaculture. Water Biology and Security, 3(4), 100290. Link to source: https://doi.org/10.1016/j.watbs.2024.100290

Credits

Lead Fellow

  • Christina Richardson, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Speed of Action
left_text_column_width
Caveats
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Improve
Solution Title
Aquaculture
Classification
Worthwhile
Lawmakers and Policymakers
Practitioners
Business Leaders
Nonprofit Leaders
Investors
Philanthropists and International Aid Agencies
Thought Leaders
Technologists and Researchers
Communities, Households, and Individuals
Updated Date

Boost Whale Restoration

Image
Image
Peatland
Coming Soon
On
Description for Social and Search
The Boost Whale Restoration solution is coming soon.
Solution in Action
Speed of Action
left_text_column_width
Caveats
left_text_column_width
Additional Benefits
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Boost
Solution Title
Whale Restoration
Classification
Worthwhile
Updated Date

Boost Large Herbivore Restoration

Image
Image
Peatland
Coming Soon
On
Description for Social and Search
The Boost Large Herbivore Restoration solution is coming soon.
Solution in Action
Speed of Action
left_text_column_width
Caveats
left_text_column_width
Additional Benefits
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Boost
Solution Title
Large Herbivore Restoration
Classification
Worthwhile
Updated Date

Deploy Waste to Energy

Image
Image
Peatland
Coming Soon
On
Description for Social and Search
The Use Waste to Energy solution is coming soon.
Solution in Action
Speed of Action
left_text_column_width
Caveats
left_text_column_width
Additional Benefits
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Deploy
Solution Title
Waste to Energy
Classification
Worthwhile
Updated Date

Boost Appliance and Equipment Efficiency

Image
Image
Washing machines on conveyer belts in a factory
Coming Soon
Off
Summary

Boosting the efficiency of appliances and equipment cuts GHG emissions by reducing the amount of electricity used to operate these devices. Efficiency improvements also lead to reduced peak demand, less strain on the electric grid, and potential utility savings for homeowners due to the reduced electricity use. Despite this potential, the increase in the total number of households and average ownership of appliances, especially in low- and middle-income countries, has offset the impact of efficiency gains and resulted in increased electricity consumption from devices globally. We conclude that Boost Appliance and Equipment Efficiency is “Worthwhile” because it functionally reduces the energy consumed by these devices, but significant leaps in efficiency and shifts in user behavior are needed to realize its full potential as a climate solution.

Description for Social and Search
Boosting the efficiency of appliances and equipment cuts GHG emissions by reducing the amount of electricity used to operate these devices.
Overview

What is our assessment?

Based on our analysis, boosting appliance and equipment efficiency is a promising strategy for reducing GHG emissions, but significant leaps in efficiency and shifts in user behavior are needed to mitigate the rebound effect and realize its impact. This potential climate solution is “Worthwhile.”

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? No
Risk Is it risky or harmful? No
Cost Is it cheap? Yes

What is it?

Appliance and equipment efficiency typically refers to larger devices in residential buildings that run on electricity, such as refrigerators, freezers, washing machines, dishwashers, dryers, and televisions. Energy-efficient appliances or equipment will consume less electricity when operated compared to inefficient devices. Therefore, boosting appliance efficiency reduces the CO₂, methane, and nitrous oxide emissions from electricity generation. As of 2022, the energy consumed by household appliances globally was more than twice the total energy used to cool both residential and nonresidential buildings, and about half the energy used for heating. To drive higher efficiency for these devices, various countries have established regional energy efficiency standards, rating systems, and labeling programs. Currently, homeowners can readily access a variety of options on the appliance market, and less efficient devices can easily be replaced. However, income levels, especially in low- and middle-income countries, may affect people’s actual ability to purchase certain appliances, although these devices are increasingly becoming cheaper.

Does it work?

Improving the efficiency of appliances and equipment functionally reduces the energy required to run these devices. Various field studies have demonstrated the effect of efficiency gains on lowering electricity consumption. However, the rise in appliance ownership per household and the growing total number of households have offset the collective climate impact expected from efficiency improvements. Globally, the number of households grew from about 1.5 billion in 2000 to 2.2 billion in 2021. Considering the concurrent increase in the global average units owned per household, the number of appliances in use has essentially doubled over the same period. For example, we estimate that over two decades, the number of television units owned grew from about 1.4 to 2.8 billion units, refrigerators grew from 0.9 to 1.7 billion units, and washing machines grew from about 0.6 to 1.1 billion units. This growth resulted in rising electricity consumption by appliances annually, from 2,880 TWh in 2000 to 5,734 TWh in 2022, which translates to a 99% global increase, largely driven by the Asia-Pacific region.

Why are we excited?

Boosting appliance and equipment efficiency allows homeowners to realize operational cost savings as a result of lower electricity consumption and utility bills. Compared to less efficient devices, using appliances with higher efficiency ratings functionally reduces peak electricity demand, alleviating strain on the electric grid. The advent of smart devices and the Internet of Things (IoT) also helps to automate the operation of these appliances, and thereby optimize their runtime while minimizing the energy consumed. Initial purchasing costs are also declining, making efficient appliances more accessible and affordable. Access to high-efficiency appliances also yields additional benefits. For example, access to energy-efficient refrigerators and freezers means that food waste can be minimized with less energy, leading to better food security. Similarly, multimedia equipment, such as television sets, offers access to critical information. Further cuts in GHG emissions are also possible as the electric grid transitions to renewable energy sources.

Why are we concerned?

Despite the potential benefits, the efficiency improvements in household appliances and equipment have not effectively translated into a positive climate impact. This is largely due to the significant rebound effect, or the increase in appliances owned by households as these devices become cheaper and more efficient. Considering the role of appliances in providing a greater quality of life, limiting the increase in appliance purchases is dismissible. The markets for appliances and equipment in many countries also still consist of pre-owned devices, which are less efficient. Some countries, such as Ghana, have established legislation to prevent the importation of pre-owned devices. This approach ensures that the appliances bought by homeowners will run on the newest, most efficient technologies. Recent findings from regions with stringent energy rating systems also suggest that regulations and programs can lead to a 50% cut in the electricity consumed by appliances. Global initiatives, such as the United for Efficiency (U4E) partnership, which seeks to shift appliance markets in low- and middle-income countries into high-efficiency devices, are increasingly needed for the potential energy savings to be realized as a climate solution.

Solution in Action

CLASP. (2023). Net zero heroes: Scaling efficient appliances for climate change mitigation, adaptation & resilience. CLASP. Link to source: https://www.clasp.ngo/wp-content/uploads/2024/01/CLASP-COP28-FullReport-V8-012424.pdf

Darshan, A., Girdhar, N., Bhojwani, R., Rastogi, K., Angalaeswari, S., Natrayan, L., & Paramasivam, P. (2022). Energy audit of a residential building to reduce energy cost and carbon footprint for sustainable development with renewable energy sources. Advances in Civil Engineering, 2022(1), 4400874. Link to source: https://doi.org/10.1155/2022/4400874

de Ayala, A., Foudi, S., Solà, M. d. M., López-Bernabé, E., & Galarraga, I. (2020). Consumers’ preferences regarding energy efficiency: A qualitative analysis based on the household and services sectors in Spain. Energy Efficiency, 14(1), 3. Link to source: https://doi.org/10.1007/s12053-020-09921-0

de Ayala, A., & Solà, M. d. M. (2022). Assessing the EU energy efficiency label for appliances: Issues, potential improvements and challenges. Energies, 15(12), 4272. Link to source: https://doi.org/10.3390/en15124272

IEA. (2022, 22 September 2022). Worldwide average household ownership of appliances and number of households in the net zero scenario, 2000-2030. Retrieved 20 April 2025 from Link to source: https://www.iea.org/data-and-statistics/charts/worldwide-average-household-ownership-of-appliances-and-number-of-households-in-the-net-zero-scenario-2000-2030

IEA. (2023). Space cooling: Net zero emissions guide. IEA. Link to source: https://www.iea.org/reports/space-cooling-2

IEA/4E TCP. (2021). Achievements of energy efficiency appliance and equipment standards and labeling programmes. IEA. Link to source: https://www.iea.org/reports/achievements-of-energy-efficiency-appliance-and-equipment-standards-and-labelling-programmes

Lane, K., & Camarasa, C. (2023, 11 July 2023). Appliances and equipment. IEA. Retrieved 13 May 2025 from Link to source: https://www.iea.org/energy-system/buildings/appliances-and-equipment

Stasiuk, K., & Maison, D. (2022). The influence of new and old energy labels on consumer judgements and decisions about household appliances. Energies, 15(4), 1260. Link to source: https://doi.org/10.3390/en15041260

United for Efficiency (U4E). (2025). About the partnership. United Nations Environment Program (UNEP). Retrieved 15 May 2025 from Link to source: https://united4efficiency.org/about-the-partnership/ 

Credits

Lead Fellow

  • Henry Igugu, Ph.D.

Contributors

  • Zoltan Nagy, Ph.D.
  • Amanda D. Smith, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Speed of Action
left_text_column_width
Caveats
left_text_column_width
Additional Benefits
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Boost
Solution Title
Appliance and Equipment Efficiency
Classification
Worthwhile
Updated Date

Use Low-Flow Fixtures

Image
Image
Water streaming from shower head
Coming Soon
Off
Summary

Low-flow fixtures reduce GHG emissions by reducing the volume of hot water that is used and therefore reducing the emissions from the energy used to heat that water. Reduced water usage also leads to fewer emissions from treating and pumping water for domestic use. Low-flow fixtures are low-cost and simple to install. They generate utility bill savings for households and support sustainable water resource management. Modern quality low-flow fixtures have resolved many of the performance issues of earlier versions. Even with significant adoption, however, the total emissions reduction potential for low-flow fixtures is relatively small. We conclude that, despite its modest emissions impact, Use Low Flow Fixtures is “Worthwhile” due to its relative ease, low cost, and additional benefits.

Description for Social and Search
Low-flow fixtures reduce GHG emissions by reducing the volume of hot water that is used and therefore reducing the emissions from the energy used to heat that water.
Overview

What is our assessment?

Based on our analysis, using low-flow fixtures is a cost-effective strategy for reducing water consumption, but has only a modest impact on GHG emissions. Therefore, this climate solution is “Worthwhile.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? No
Risk Is it risky or harmful? No
Cost Is it cheap? Yes

What is it?

Low-flow fixtures lessen the total consumption of water by reducing flow rates through a household faucet or shower. Less hot water use means fewer emissions from the energy source used to heat the water, and it also means fewer emissions from pumping and treating tap water. Heating water for showers, sinks, and other domestic appliances is often the second largest source of emissions from buildings after space heating. Modern low-flow showerheads can produce comparable pressure and coverage to traditional showerheads through aeration and/or laminar flow. Aerators for faucets and low-flow showerheads are relatively low-cost investments that users can install themselves.

Does it work?

Low-flow fixtures reduce emissions from heating, delivering, and treating water by reducing the hot water consumption. There is ample evidence for water savings with low-flow fixtures, as well as for the linkage between quantity and source of energy used for water heating and GHG emissions. Additionally, there is substantial research on the emissions from treating and pumping water, which can be reduced through water conservation. Low-flow fixtures are readily available, and performance labels are available to help consumers select quality products.

Why are we excited?

Low-flow fixtures conserve water, which reduces emissions, reduces energy demand, saves consumers money, and helps with sustainable water resource management. Households that adopt low-flow fixtures can enjoy significant utility bill savings because these fixtures reduce both water consumption and the energy used to heat water in the home. Faucet aerators also produce a smoother water stream with less splashing, and along with low-flow showerheads, are low-cost and simple to install. Household water conservation practices, such as low-flow fixtures, can help with regional sustainable water resource management and defer infrastructure expansion projects. This is particularly important in areas where water resources are increasingly strained due to climate change, growing populations, and other factors. In some regions, community water conservation efforts have had measurable impacts on water treatment costs, resulting in lower water rates for consumers.  

Why are we concerned?

Even with widespread adoption, low-flow fixtures would have a relatively small impact on GHG emissions. Moreover, the low cost and ease of replacement mean that low-flow fixtures can be easily reverted to less efficient fixtures, eliminating the emissions impact and other benefits. Lastly, although modern quality low-flow showerheads are comparable to traditional fixtures, the poor quality of early low-flow showerheads may have contributed to decreasing levels of adoption in some areas.

Solution in Action

Alliance for water efficiency. (2017). Conservation keeps rates low in Tucson, Arizona. Link to source: https://allianceforwaterefficiency.org/wp-content/uploads/2017/06/AWE_Tucson_ConsRates_FactSheet_final.pdf

Dieu-Hang, T., Grafton, R. Q., Martínez-Espiñeira, R., & Garcia-Valiñas, M. (2017). Household adoption of energy and water-efficient appliances: An analysis of attitudes, labelling and complementary green behaviours in selected OECD countries. Journal of Environmental Management, 197, 140–150. Link to source: https://doi.org/10.1016/j.jenvman.2017.03.070

Environmental protection agency. (2022). WaterSense performance overview: Showerheads. Link to source: https://www.epa.gov/system/files/documents/2022-05/ws-products-perfomance-showerheads.pdf

Kenway, S. J., Pamminger, F., Yan, G., Hall, R., Lam, K. L., Skinner, R., Olsson, G., Satur, P., & Allan, J. (2023). Opportunities and challenges of tackling Scope 3 “Indirect” emissions from residential hot water. Water Research X, 21, 100192. Link to source: https://doi.org/10.1016/j.wroa.2023.100192

Maas, A., Puri, R., & Goemans, C. (2024). A review of residential water conservation policies and attempts to measure their effectiveness. PLOS Water, 3(8), e0000278. Link to source: https://doi.org/10.1371/journal.pwat.0000278

Paraschiv, S., Paraschiv, L. S., & Serban, A. (2023). An overview of energy intensity of drinking water production and wastewater treatment. Energy Reports, 9, 118–123. Link to source: https://doi.org/10.1016/j.egyr.2023.08.074

Pomianowski, M. Z., Johra, H., Marszal-Pomianowska, A., & Zhang, C. (2020). Sustainable and energy-efficient domestic hot water systems: A review. Renewable and Sustainable Energy Reviews, 128, 109900. Link to source: https://doi.org/10.1016/j.rser.2020.109900

Tomberg, L. (2024). Resource conservation through improved efficiency, behavioral change, or both: Willingness to pay for (smart) efficient shower heads. Resources, Conservation and Recycling, 203, 107387. Link to source: https://doi.org/10.1016/j.resconrec.2023.107387

Yateh, M., Li, F., Tang, Y., Li, C., & Xu, B. (2024). Energy consumption and carbon emissions management in drinking water treatment plants: A systematic review. Journal of Cleaner Production, 437, 140688. Link to source: https://doi.org/10.1016/j.jclepro.2024.140688

Zhou, Y., Essayeh, C., Darby, S., & Morstyn, T. (2024). Evaluating the social benefits and network costs of heat pumps as an energy crisis intervention. iScience, 27(2), Article 2. Link to source: https://doi.org/10.1016/j.isci.2024.108854 

Credits

Lead Fellow

  • Heather McDiarmid, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Speed of Action
left_text_column_width
Caveats
left_text_column_width
Additional Benefits
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Use
Solution Title
Low-Flow Fixtures
Classification
Worthwhile
Updated Date

Reduce Overfishing

Image
Image
An image of a fishing boat at sunset
Coming Soon
On
Summary

Reduce Overfishing refers to the use of management actions that decrease fishing effort and therefore cut CO₂ emissions from fishing vessel fuel use on overfished stocks. Advantages include the potential to replenish depleted fish stocks, support ecosystem health, and enhance long-term food and job security. Disadvantages include the short-term reductions in fishing effort needed to allow systems to recover, which could impact local livelihoods and economies. While these interventions are not expected to reach globally meaningful levels of emissions reductions (>0.1 Gt CO₂‑eq/yr ), we conclude that Reduce Overfishing is “Worthwhile” with important ecosystem and social benefits.

Description for Social and Search
The Improve Fisheries solution is coming soon.
Overview

What is our assessment?

Our analysis concludes that, despite its limited global impact for reducing emissions, Reduce Overfishing is a “Worthwhile” climate solution that has other important benefits for ecosystem health and long-term food security.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? No
Risk Is it risky or harmful? No
Cost Is it cheap? ?

What is it?

Reducing overfishing lowers fuel use and CO₂ emissions from wild capture fishing vessels by reducing fishing effort on overfished stocks. This is typically achieved through management actions, such as seasonal closures, gear restrictions, and catch limits. Fishing effort, whether measured as the hours spent fishing or distance traveled, is generally proportional to fuel use. In addition to immediate reductions in emissions, reducing overfishing can allow overfished stocks to recover, which can lead to reduced future emissions since fuel use is lowered when fish are easier to catch and harvested sustainably.

Does it work?

Reducing fishing effort in locations with depleted and overfished wild fish stocks is expected to reduce emissions from fishing vessels. When stocks are overfished, fishers must exert additional effort, traveling further and/or searching longer to make the same catch, which increases fuel use and CO₂ emissions. Reducing overfishing through management actions, such as harvest control rules, gear restrictions, seasonal closures, stronger enforcement of existing regulations, and establishment of marine protected areas, can help fish stocks recover. Other policy tools, such as reducing harmful fuel subsidies that currently enable many otherwise unprofitable fishing fleets, are also likely to result in lower fuel use and CO₂ emissions. Healthy fish stocks can be caught with lower fishing effort, translating to future fuel savings and reduced CO₂ emissions. Global estimates suggest that reductions in overfishing could avoid up to 0.08 Gt CO₂‑eq/yr, representing almost half of the entire capture fisheries sector's annual emissions (0.18 Gt CO₂‑eq/yr ).

Why are we excited?

Currently, overfishing affects more than 35% of global wild marine fish stocks, increasing by 1%, on average, every year. Reducing overfishing not only lowers fuel use and emissions but also allows overfished stocks to recover. Healthy fish stocks strengthen marine food webs and contribute to ecosystem resilience and biodiversity. Overfishing has widespread consequences for diverse marine ecosystems, such as kelp forests, where declines in fish have led to overgrazing of the kelp by sea urchins. Over time, management interventions will also likely improve the sustainability and long-term reliability of coastal livelihoods and food security by supporting sustainable fisheries.

Why are we concerned?

Policy and management tools for reducing overfishing and, by extension, fishing-related emissions come with some challenges. For instance, management measures or legal protections may not be fully effective if implementation or enforcement is weak. Management and enforcement can be particularly challenging on the high seas, where jurisdiction is limited or shared across many nations, and where illegal, unreported, and unregulated fishing can be widespread. Even when effective, fish stock recovery can take years to decades, and the costs and trade-offs are unlikely to be evenly distributed across fishing fleets. In the short term, efforts to reduce overfishing could create economic challenges for small-scale fishers who may have fewer resources and less capacity to adapt to management restrictions.

Andersen, N. F., Cavan, E. L., Cheung, W. W., Martin, A. H., Saba, G. K., & Sumaila, U. R. (2024). Good fisheries management is good carbon management. npj Ocean Sustainability3(1), 17. Link to source: https://doi.org/10.1038/s44183-024-00053-x

Bastardie, F., Hornborg, S., Ziegler, F., Gislason, H., & Eigaard, O. R. (2022). Reducing the fuel use intensity of fisheries: through efficient fishing techniques and recovered fish stocks. Frontiers in Marine Science9, 817335. Link to source: https://doi.org/10.3389/fmars.2022.817335

Food and Agriculture Organization of the United Nations. (2018). The state of world fisheries and aquaculture. Food and Agriculture Organization of the United Nations. Link to source: https://openknowledge.fao.org/handle/20.500.14283/i9540en

Food and Agriculture Organization of the United Nations. (2024). The State of World Fisheries and Aquaculture 2024 – Blue Transformation in action. Food and Agriculture Organization of the United Nations. Link to source: https://openknowledge.fao.org/handle/20.500.14283/cd0683en

Gaines, S. D., Costello, C., Owashi, B., Mangin, T., Bone, J., Molinos, J. G., ... & Ovando, D. (2018). Improved fisheries management could offset many negative effects of climate change. Science Advances, 4(8), eaao1378. Link to source: https://doi.org/10.1126/sciadv.aao1378

Gephart, J. A., Henriksson, P. J., Parker, R. W., Shepon, A., Gorospe, K. D., Bergman, K., ... & Troell, M. (2021). Environmental performance of blue foods. Nature597(7876), 360-365. Link to source: https://doi.org/10.1038/s41586-021-03889-2

Gulbrandsen, O. (2012). Fuel savings for small fishing vessels. Food and Agriculture Organization of the United Nations. Link to source: https://www.fao.org/4/i2461e/i2461e.pdf

Hilborn, R., Amoroso, R., Collie, J., Hiddink, J. G., Kaiser, M. J., Mazor, T., ... & Suuronen, P. (2023). Evaluating the sustainability and environmental impacts of trawling compared to other food production systems. ICES Journal of Marine Science80(6), 1567-1579. Link to source: https://doi.org/10.1093/icesjms/fsad115

Hoegh-Guldberg, O., Caldeira, K., Chopin, T., Gaines, S., Haugan, P., Hemer, M., ... & Tyedmers, P. (2023). The ocean as a solution to climate change: five opportunities for action. In The blue compendium: From knowledge to action for a sustainable ocean economy (pp. 619-680). Cham: Springer International Publishing. Link to source: https://oceanpanel.org/wp-content/uploads/2023/09/Full-Report_Ocean-Climate-Solutions-Update-1.pdf

Johnson, T. (2009). Fuel-Saving Measures for Fishing Industry Vessels. University of Alaska Fairbanks, Alaska Sea Grant Marine Advisory Program. Link to source: https://alaskaseagrant.org/wp-content/uploads/2022/03/ASG-57PDF-Fuel-Saving-Measures-for.pdf

Ling, S. D., Johnson, C. R., Frusher, S. D., & Ridgway, K. (2009). Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift. Proceedings of the National Academy of Sciences, 106(52), 22341-22345. Link to source: https://doi.org/10.1073/pnas.0907529106

Machado, F. L. V., Halmenschlager, V., Abdallah, P. R., da Silva Teixeira, G., & Sumaila, U. R. (2021). The relation between fishing subsidies and CO2 emissions in the fisheries sector. Ecological Economics185, 107057. Link to source: https://doi.org/10.1016/j.ecolecon.2021.107057

Parker, R. W., Blanchard, J. L., Gardner, C., Green, B. S., Hartmann, K., Tyedmers, P. H., & Watson, R. A. (2018). Fuel use and greenhouse gas emissions of world fisheries. Nature Climate Change8(4), 333-337. Link to source: https://doi.org/10.1038/s41558-018-0117-x

Pauly, D., Christensen, V., Dalsgaard, J., Froese, R., & Torres Jr, F. (1998). Fishing down marine food webs. Science, 279(5352), 860-863. Link to source: https://doi.org/10.1126/science.279.5352.860

Ritchie, H., & Roser, M. (2021). Fish and overfishing. Our World in Data. Link to source: https://ourworldindata.org/fish-and-overfishing

Sharma, R., Barange, M., Agostini, V., Barros, P., Gutierrez, N.L., Vasconcellos, M., Fernandez Reguera, D., Tiffay, C., & Levontin, P., (Eds.). (2025). Review of the state of world marine fishery resources – 2025. FAO Fisheries and Aquaculture Technical Paper, No. 721. Rome. FAO. Link to source: https://doi.org/10.4060/cd5538en

Sumaila, U. R., Ebrahim, N., Schuhbauer, A., Skerritt, D., Li, Y., Kim, H. S., ... & Pauly, D. (2019). Updated estimates and analysis of global fisheries subsidies. Marine Policy109, 103695. Link to source: https://doi.org/10.1016/j.marpol.2019.103695

Sumaila, U. R., & Tai, T. C. (2020). End overfishing and increase the resilience of the ocean to climate change. Frontiers in Marine Science, 7, 523. Link to source: https://doi.org/10.3389/fmars.2020.00523

United Nations Global Compact & World Wildlife Fund. (2022). Setting science-based targets in the seafood sector: Best practices to dateLink to source: https://unglobalcompact.org/library/6050

World Bank. (2017). The sunken billions revisited: Progress and challenges in global marine fisheries. World Bank Publications. Link to source: http://hdl.handle.net/10986/24056

Credits

Lead Fellow

  • Christina Richardson, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Action Word
Reduce
Solution Title
Overfishing
Classification
Worthwhile
Updated Date

Improve Manure Management

Image
Image
An image of a manure pit in an agricultural field
Coming Soon
On
Summary

Improved manure management refers to the use of impermeable covers and physical or chemical treatments applied during the storage and processing of wet manure. These techniques can reduce methane emissions under anaerobic storage conditions and nitrous oxide emissions under aerobic conditions. They offer multiple environmental benefits, including reduced air pollution, reduced nutrient leaching and eutrophication of downstream aquatic systems, and reduced demand for energy-intensive synthetic fertilizers. Disadvantages include a relatively small climate impact and high costs. Even at an optimistic level of adoption, the climate impact is unlikely to be globally meaningful (<0.1 Gt CO₂‑eq/yr ). Despite this modest climate impact, we conclude that Improve Manure Management is a “Worthwhile” solution.

Description for Social and Search
The Improve Manure Management solution is coming soon.
Overview

What is our assessment? 

Based on our analysis, improved manure management using impermeable covers and physical or chemical treatments will reduce emissions, although not by a globally meaningful amount. However, because these manure management techniques are broadly available, we conclude this climate solution is “Worthwhile”.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? Yes
Impact Is it big enough to matter? No
Risk Is it risky or harmful? No
Cost Is it cheap? ?

What is it? 

Manure generated from industrial livestock production contains significant quantities of organic carbon and nitrogen. Under low-oxygen conditions, bacteria convert organic material in manure to methane through anaerobic decomposition. Liquid manure, particularly from pigs and cows, produces significant quantities of methane. In oxygen-rich conditions, organic nitrogen in manure undergoes chemical reactions to produce nitrous oxide. Once produced, these GHGs diffuse towards the surface of the manure storage tank, where they are emitted into the atmosphere.

Improved manure management interrupts the production or release of methane and nitrous oxide through a structural barrier, or physical or chemical treatment processes. Manure storage covers made from impermeable synthetic materials effectively prevent the release of GHGs, and can be utilized in conjunction with biogas systems for energy generation. Chemical treatments, such as acidification and the addition of additives, suppress microbial activity, thereby inhibiting methane and nitrous oxide production. Physical processes, such as aeration and temperature reduction, similarly limit optimal conditions for microbial growth. Separating the solids and liquids from manure can also reduce the potential for methane production, enabling more effective solutions such as composting and anaerobic digestion.

Does it work? 

Available technologies for manure management are mature and market-ready. However, empirical evidence of their effectiveness for reducing methane emissions is limited. Pilot studies indicate high effectiveness of manure acidification, moderate effectiveness of impermeable synthetic covers, and low effectiveness of manure additives. Except for the use of natural and synthetic impermeable covers, the overall adoption of these techniques is low. 

Why are we excited? 

Improved manure management can provide environmental benefits by reducing air pollution, preventing nutrient leaching from organic solids that settle into sludge, mitigating eutrophication in downstream aquatic ecosystems, and preventing soil acidification. In the food system, manure management allows for better alignment between crop needs and natural fertilizer characteristics. Since hauling liquid manure is expensive, manure storage and treatment methods promote efficient nutrient cycling and reduce the need for energy-intensive synthetic fertilizers. Abated methane in manure also limits ground-level ozone production upon application, thereby improving crop yields.

At the farm scale, the wide range of treatment options allows for a high level of customization in the manure management process to achieve joint goals of nutrient management, revenue generation, and emission reductions. Covers also directly mitigate risks to farmworker health and safety from manure handling, and manure treatment can further limit exposure to irritants and noxious gases, improving the health of surrounding communities.

Why are we concerned?

Compared to no treatment and other manure-related solutions, such as composting and anaerobic digesters, evidence for the effectiveness of impermeable covers and manure treatment technologies is limited. At realistic levels of adoption, improving manure management is unlikely to have a globally meaningful climate impact (<0.1 Gt CO₂‑eq/yr ). High costs are also a key barrier to wider adoption, ranging from US$110–145/t CO₂‑eq for synthetic covers to US$500–3,000/t CO₂‑eq for other treatments. 

Ambikapathi, R., Periyasamy, D., Ramesh, P., Avudainayagam, S., Makoto, W., & Evgenios, A. (2023). Effect of ozone stress on crop productivity: A threat to food security. Environmental Research, 236, 116816. doi: 10.1016/j.envres.2023.116816

Ambrose, H. W., Dalby, F. R., Feilberg, A., & Kofoed, M. V. W. (2023). Additives and methods for the mitigation of methane emission from stored liquid manure. Biosystems Engineering, 229, 209-245. doi: 10.1016/j.biosystemseng.2023.03.015

Bijay, S., & Craswell, E. (2021). Fertilizers and nitrate pollution of surface and ground water: an increasingly pervasive global problem. SN Applied Sciences, 3(4). doi: 10.1007/s42452-021-04521-8

Fangueiro, D., Hjorth, M., & Gioelli, F. (2015). Acidification of animal slurry--a review. J Environ Manage, 149, 46-56. doi: 10.1016/j.jenvman.2014.10.001

FAO. (2023a). Methane emissions in livestock and rice systems – Sources, quantification, mitigation and metrics. Rome. doi: 10.4060/cc7607en

FAO. (2023b). Pathways towards lower emissions – A global assessment of the greenhouse gas emissions and mitigation options from livestock agrifood systems. doi: 10.4060/cc9029en

Grossi, G., Goglio, P., Vitali, A., & Williams, A. G. (2019). Livestock and climate change: impact of livestock on climate and mitigation strategies. Anim Front, 9(1), 69-76. doi: 10.1093/af/vfy034

Harrison, M. T., Cullen, B. R., Mayberry, D. E., Cowie, A. L., Bilotto, F., Badgery, W. B., Liu, K., Davison, T., Christie, K. M., Muleke, A., & Eckard, R. J. (2021). Carbon myopia: The urgent need for integrated social, economic and environmental action in the livestock sector. Glob Chang Biol, 27(22), 5726-5761. doi: 10.1111/gcb.15816

Hegde, S., Searchinger, T., & Díaz, M. J. (2025). Opportunities for Methane Mitigation in Agriculture: Technological, Economic and Regulatory Considerations. World Resources Institute: Washington DC. doi: 10.46830/wrirpt.23.00110

Hou, Y., Velthof, G. L., & Oenema, O. (2015). Mitigation of ammonia, nitrous oxide and methane emissions from manure management chains: a meta-analysis and integrated assessment. Glob Chang Biol, 21(3), 1293-1312. doi: 10.1111/gcb.12767

Kanter, D. R., & Brownlie, W. J. (2019). Joint nitrogen and phosphorus management for sustainable development and climate goals. Environmental Science & Policy, 92, 1-8. doi: 10.1016/j.envsci.2018.10.020

Kupper, T., Häni, C., Neftel, A., Kincaid, C., Bühler, M., Amon, B., & VanderZaag, A. (2020). Ammonia and greenhouse gas emissions from slurry storage - A review. Agriculture, Ecosystems and Environment, 300(106963). doi: 10.1016/j.agee.2020.106963

Mohankumar Sajeev, E. P., Winiwarter, W., & Amon, B. (2018). Greenhouse Gas and Ammonia Emissions from Different Stages of Liquid Manure Management Chains: Abatement Options and Emission Interactions. J Environ Qual, 47(1), 30-41. doi: 10.2134/jeq2017.05.0199

Montes, F., Meinen, R., Dell, C., Rotz, A., Hristov, A. N., Oh, J., . . . Dijkstra, J. (2013). SPECIAL TOPICS—Mitigation of methane and nitrous oxide emissions from animal operations: II. A review of manure management mitigation options. J. Anim. Sci, 91, 5070-5094. doi: 10.2527/jas.2013-6584

Mukherji, A., Arndt, C., Arango, J., Flintan, F., Derera, J., Francesconi, W., Jones, S. Loboguerrero, A. M., Merrey, D., Mockshell, J., Quintero, M., Mulat, D. G., Ringler, C., Ronchi, L., Sanchez, M. E. N., Sapkota, T., & Thilsted, S. (2023). Achieving agricultural breakthrough: A deep dive into seven technological areas. Montpellier, France. Retrieved from: www.hdl.handle.net/10568/131852.

Niles, M. T., Wiltshire, S., Lombard, J., Branan, M., Vuolo, M., Chintala, R., & Tricarico, J. (2022). Manure management strategies are interconnected with complexity across U.S. dairy farms. PLoS One, 17(6), e0267731. doi: 10.1371/journal.pone.0267731

Nour, M. M., Field, W. E., Ni, J.-Q., & Cheng, Y.-H. (2021). Farm-Related Injuries and Fatalities Involving Children, Youth, and Young Workers during Manure Storage, Handling, and Transport. Journal of Agromedicine, 26(3), 323--333. doi: 10.1080/1059924X.2020.1795034

Overmeyer, V., Trimborn, M., Clemens, J., Holscher, R., & Buscher, W. (2023). Acidification of slurry to reduce ammonia and methane emissions: Deployment of a retrofittable system in fattening pig barns. J Environ Manage, 331, 117263. doi: 10.1016/j.jenvman.2023.117263

Park, J., Kang, T., Heo, Y., Lee, K., Kim, K., Lee, K., & Yoon, C. (2020). Evaluation of Short-Term Exposure Levels on Ammonia and Hydrogen Sulfide During Manure-Handling Processes at Livestock Farms. Saf Health Work, 11(1), 109-117. doi: 10.1016/j.shaw.2019.12.007

Sokolov, V., VanderZaag, A., Habtewold, J., Dunfield, K., Wagner-Riddle, C., Venkiteswaran, J. J., & Gordon, R. (2019). Greenhouse Gas Mitigation through Dairy Manure Acidification. J Environ Qual, 48(5), 1435-1443. doi: 10.2134/jeq2018.10.0355

VanderZaag, A., Amon, B., Bittman, S., & Kuczyński, T. (2015). Ammonia Abatement with Manure Storage and Processing Techniques. In Costs of Ammonia Abatement and the Climate Co-Benefits (pp. 75-112). doi: 10.1007/978-94-017-9722-1

Wang, Y., Dong, H., Zhu, Z., Gerber, P. J., Xin, H., Smith, P., Opio, C., Steinfeld, H., & Chadwick, D. (2017). Mitigating Greenhouse Gas and Ammonia Emissions from Swine Manure Management: A System Analysis. Environ Sci Technol, 51(8), 4503-4511. doi: 10.1021/acs.est.6b06430

Wyer, K. E., Kelleghan, D. B., Blanes-Vidal, V., Schauberger, G., & Curran, T. P. (2022). Ammonia emissions from agriculture and their contribution to fine particulate matter: A review of implications for human health. J Environ Manage, 323, 116285. doi: 10.1016/j.jenvman.2022.116285

Credits

Lead Fellow

  • Aishwarya Venkat, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Action Word
Improve
Solution Title
Manure Management
Classification
Worthwhile
Updated Date
Subscribe to Worthwhile