Investigation of biomass blending ratios for optimal biochar's soil application

Due to the rapid growth of population, urbanization and economic development, global municipal waste generation is expected to increase by nearly 70% to 3.4 billion tonnes by 2050. The mismanagement of these wastes results in the deterioration of soil, air, and water quality, causing serious health problems. As such, investigating waste valorization routes becomes more essential to alleviate the concerns associated with the burden of wastes. In this study, 10 different types of biomass used to produce biochar through pyrolysis were investigated; namely camel manure (CM), date pits (DP), sewage sludge (SS), coffee waste (CW), cattle manure (CM), poultry litter (PL), cabbage waste (CB), cucumber waste (CU), tomato waste (TM), and carrot waste (CR). Techno-economic and environmental analyses were performed from “cradle to grave”, covering the key biochar production stages from acquisition of biomass, transportation, plant's construction, pre-processing, pyrolysis, and lastly the end-use of biochar as soil enhancer. The cost and emissions savings using biochar as an alternative to commercial fertilizers were evaluated for the different biomass scenarios. Finally, an optimization model was developed to select the optimal biomass blending ratio for two scenarios to maximize the savings, which was then solved using MATLAB. The findings of this study indicated that the optimal biomass blend for maximizing cost, energy and emissions savings shall consist of the following proportions: 50% TM, 14-15% CW and PL, 5 – 10% CM and CU, 2.5% CT, 1.8-1.9% CB and DP, 1.2% CR and 0 – 0.6% SS. Future studies may involve more types of biomasses, additional optimization objectives, and may target multiple biochar's end-use applications.