High-efficiency recycling mode of agroforest wastes and its benefit analysis

Abstract: China has abundant agroforestry residue resources. According to the statistics, the amount of crop straw and forestry residue reached 900 million and 300 million tons, respectively. At present, the use of agroforestry residues mainly includes fertilizer, raw material, energy, and feed. Realizing the efficient recycling of agroforestry waste resources is an important way to increase the added value of agroforestry, promote the green development of agroforestry, improve the rural energy structure, and enhance the rural human settlement environment. Biomass pyrolysis poly-generation based on slow pyrolysis technology of biomass, through pyrolysis gas purification and co-production technology integration, produces a wide range of products in clean gas, biochar, pyrolysis oil, vinegar, electricity and hot water. Biomass pyrolysis gas is clean and renewable, and it is an important energy source for the replacement of bulk coal in rural areas. Biochar can improve soil, and can also be processed to produce high quality energy products. Biomass pyrolysis poly-generation is one of the important ways to comprehensively utilize agricultural and forestry wastes, which can further enhance the comprehensive benefits of the development and utilization of agricultural and forestry waste resources, and have a good prospect for popularization and application. Based on the biomass pyrolysis carbon gas co-production technology, this paper constructs an energy-efficient resource efficient recycling application model for agriculture and forestry waste. Straw biochar is used for returning to the field, and wood charcoal for heating after molding. The pyrolysis gas is used for residents' cooking and hot water. The pyrolysis oil is burned for system heating, and the wood vinegar is diluted for insecticide. Under the conditions of 5 500 to 6 000 hours of operation, the Qiannanyu Pyrolysis Poly-generation Demonstration Project processes 2 500 t of various agricultural and forestry wastes annually, produces 700 t of biochar (including 150 t of straw biochar and 550 t of wood biochar), and produces more than 200 000 m3 of pyrolysis gas. The woody charcoal and pyrolysis gas can meet the requirements of 386 farmers in the village for winter heating and hot water for the whole year. The straw biochar is mixed with human and animal manure, all of which are used for returning to the field. The raw material purchase adopts the method of woody charcoal exchange, 5 t agricultural and forestry wastes are exchanged for 1 t carbon base fertilizer or woody charcoal for heating, and the pyrolysis gas is sold to the villagers at the price of 0.9 yuan/m3. The project is sustainable, reproducible and has significant social and environmental benefits, and it realizes a high value utilization of agroforestry waste, improves the energy structure of rural areas, and promotes the sustainable development of agriculture.