Decarbonisation Technology May 2022 Issue

(1) best management practices that achieve both mitigation and food security, and (2) incentives, technical support mechanisms, and enabling conditions to overcome the barriers that men and women farmers face in using new practices (IRRI, 2021a). Reducing methane from livestock In many countries, there is considerable scope for improvement in the efficiency of livestock farming, leading to higher production levels and reduced methane emissions (see Figure 3 ). Such measures include: • Improved feed availability and quality • Better herd and health management and husbandry • Manure management. The CCAC found that these measures could reduce methane emissions by 8.6 million tonnes (Mt) per year, though with considerable (4.5- 47.5%) country to country variation. CCAC also noted that whilst such efficiency measures may reduce the emissions per unit (animal), total emissions may still increase due to forecast increases in production. Two emerging trends that could temper the forecast increases in global meat production are the move to healthier diets with more plant proteins and the use of precision fermentation to produce 'alternative animal' proteins. Rethinkx, a think tank, suggests that alternative proteins will lead to a 50% reduction in the number of cows in the US by 2030 (Rethinkx Team, 2019). Whilst thought-provoking, it would be unwise to count on such a disruption in human dietary behaviour delivering a reduction in global methane emissions by 2030. Agriculture (GACSA) is promoting integrated manure management as a means to improve soil health, along with composting and anaerobic digestion to reduce emissions of both methane and nitrous oxide, another potent GHG (FAO, 2022). With the world’s largest domesticated animal population, China made a commitment in its Nationally Determined Contribution (NDC) to develop low-carbon agriculture and reduce GHG emissions through manure management. Manure and waste management The Global Alliance for Climate Smart

CCAC is working with the Chinese Academy of Agricultural Sciences to incorporate methane mitigation measures into China’s 14th Five- Year Plan (2021-25) and update China’s NDC (CCAC, 2020). Among other measures, CCAC is promoting farm-scale anaerobic digestion to control methane emissions from manure. Bioenergy methane solutions: anaerobic digestion Anaerobic digestion (AD) is a proven and energy-efficient method to decompose organic matter. Anaerobic bacteria digest the organic matter to produce biogas (a mix of methane and CO 2 with small amounts of other gases) along with an organic residue called digestate, a nutrient-rich fertiliser or soil improver (Global Methane Initiative, 2016). Small-scale digesters are widespread in Asia in households and farms. More than 100 million people in rural China use biogas for cooking, lighting, and heating (Drawdown, 2019c). In China, mono-digesters that use animal manure as feedstock are the most common type of anaerobic digester. However, Zheng et al. , recognise the tremendous opportunity to upgrade biogas production in China and other developing countries by adopting modern technologies and management practices (Zheng, et al. , 2020). Co-digestion biogas units are common in Europe and the US, combining a broader range of organic feedstocks, such as manure, food waste (processing, distribution, and consumer- generated materials), energy crops, crop residues, as well as fats, oils, and greases. Co- digestion biogas units are more efficient and give higher yields of biogas. Methane in the biogas can be purified (CO2 removed) to produce biomethane, which can then be inserted into natural gas grids, used for electricity production, or used as a vehicle fuel (see Figure 4 ). The EPA currently lists 317 anaerobic digester projects operating on livestock farms in the US (EPA, 2022). In Europe, most local authorities use anaerobic digestion technology to treat sewage in wastewater. In 2011, over 70% of municipal wastewater treatment plants in the UK used anaerobic digesters to produce energy (DEFRA, 2011). Municipal solid waste (MSW) digesters