Potentiality of agricultural biomass energy for greenhouse gas emission reduction

Abstract: Agricultural wastes are cost-effective, renewable, and abundant in China, such as crop straw and livestock manure. Biomass energy technologies can be widely utilized for the effective disposal of agricultural waste resources. The environmental pollution of agricultural wastes can be reduced by the emission of greenhouse gas (GHG), due to the traditiopnal incineration or disorderly stacking. It is also likely to replace fossil energy for much fewer CO2 emissions during soil carbon sequestration in the future. In this study, a systematic evaluation was made for the potential reduction in the GHG from the agriculture biomass energy, according to the "2006 IPCC Guidelines for National Greenhouse Gas Inventories" and the Life Cycle Assessment (LCA). The GHG emission factors were also calculated in the eight biomass energy technologies from the three scenarios, including the energy consumption emissions during the conversion and utilization of agricultural biomass energy, the deduction of fossil energy emissions reduction, and the carbon sinks of by-products to the soil. The potential of agricultural biomass energy to replace fossil energy and the contribution of GHG emission reduction were then predicted under three scenarios using the resource endowment and energy utilization of straw and livestock manure. The results showed that the largest contributions of GHG reduction were achieved by the pyrolysis of carbon gas for cogeneration, and large-scale biogas/biogas, followed by the molding fuels, bundle heating, biomass power generation, carbonization, and fuel ethanol. There was only a relatively small contribution of household biogas to the emissions reduction. The contributions of GHG emission reduction were 3.47, 3.20, 2.57, 2.63, 2.58, 2.48, and 2.42 t/t for the eight technologies of biomass energy, respectively. The potential of agricultural biomass energy to the reduction of GHG emissions was evaluated under three scenarios, including the existing policies and planning, technological improvement, as well as the energy demand structure. It was found that the potential to replace fossil energy in 2030 and 2060 were 6 490×104-7 664×104 t and 9 073×104-10 763×104 t, respectively, where the contributions of GHG emission reduction were 1.97×108-2.34×108 t and 2.79×108-3.35×108 t, respectively. Based on the principle of agricultural waste priority, the energy utilization potential of agricultural waste was predicted conservatively. It is predicted that the energy utilization potential of crop straw in 2030 will be 1.2×108 t, accounting for 13.3% of the total straw resources. The resource potential of energy utilization of livestock manure was 2.12×108 t, accounting for 11.2% of the total resources of livestock manure. By 2060, the energy utilization potential of crop straw resources will remain stable, and the energy utilization amount of livestock manure will increase to 3.27×108 t, accounting for about 15.3% of the total livestock manure. Agricultural biomass energy can not only replace fossil fuels as a clean and renewable energy, promote the reduction of energy carbon intensity, but also through the return of by-products to the field, improve soil carbon sink, achieve negative carbon emissions, GHG emission reduction potential is huge. The research provides data support for achieving the goals of carbon peak and carbon neutral in agriculture and rural areas.