Mon, Aug 15, 2022: 3:45 PM-4:00 PM
513D
Background/Question/MethodsThe leading source of anthropogenic methane (CH4) emissions is livestock. In intensive dairy systems, up to half of CH4 emissions come from manure management. Recent policies targeting CH4 emissions, such as California's short-lived climate pollutant reduction law (SB 1383) and the Global Methane Pledge, will require a significant reduction in livestock CH4 by 2030. However, strategies aimed at reducing CH4 from dairy manure typically focus on the liquid portion of manure, whereas stockpiled solids can remain a large source of CH4. To address this problem, we asked the question: what role can biochar-composting of dairy manure solids, a novel methane (CH4) mitigation strategy, play in meeting California's short-lived climate pollutant reduction law (SB 1383) and the Global Methane Pledge? We answered this question by measuring daily greenhouse gas (GHG) fluxes during a field-scale biochar-composting experiment, incorporating experimental flux data into the first life-cycle assessment (LCA) of a biochar-composting dairy manure management system, and using LCA results to estimate the role that biochar-composting can play in meeting CH4 goals in California and globally.
Results/ConclusionsWe find that adding 6% biochar to composting dairy manure reduces CH4 by 81% compared to compost without biochar. Using experimental data, we conduct the first life-cycle assessment (LCA) of a biochar-composting solid dairy manure management system and show that biochar-composting has a net global warming potential of -535 kg CO2e Mg-1 manure compared to -194 kg CO2e Mg-1 for composting and 102 kg CO2e Mg-1 for stockpiling. Using our LCA results, we estimate that when biochar-composting is scaled up in intensive dairy systems globally, the technical CH4 mitigation potential from dairy manure increases from 4.54 Tg CH4 yr-1 to 6.13 Tg CH4 yr-1, and the technical net greenhouse gas mitigation potential nearly doubles, increasing from 154 Tg CO2e yr-1 to 297 Tg CO2e yr-1. This timely study comes as governments and farmers begin ramping up efforts to cut CH4 emissions by the end of the decade. We believe this work can aid policymakers in this mission by demonstrating the potential of a promising, novel strategy to reduce emissions from livestock, the largest anthropogenic source of CH4.
Results/ConclusionsWe find that adding 6% biochar to composting dairy manure reduces CH4 by 81% compared to compost without biochar. Using experimental data, we conduct the first life-cycle assessment (LCA) of a biochar-composting solid dairy manure management system and show that biochar-composting has a net global warming potential of -535 kg CO2e Mg-1 manure compared to -194 kg CO2e Mg-1 for composting and 102 kg CO2e Mg-1 for stockpiling. Using our LCA results, we estimate that when biochar-composting is scaled up in intensive dairy systems globally, the technical CH4 mitigation potential from dairy manure increases from 4.54 Tg CH4 yr-1 to 6.13 Tg CH4 yr-1, and the technical net greenhouse gas mitigation potential nearly doubles, increasing from 154 Tg CO2e yr-1 to 297 Tg CO2e yr-1. This timely study comes as governments and farmers begin ramping up efforts to cut CH4 emissions by the end of the decade. We believe this work can aid policymakers in this mission by demonstrating the potential of a promising, novel strategy to reduce emissions from livestock, the largest anthropogenic source of CH4.