This paper assesses agricultural residues available for biogas production in smallholder farming systems in the KwaZulu-Natal and Limpopo provinces of South Africa, during 2017–2018. Biomass estimations were done using a combination of smallholder surveys, publicly available data, and literature models, and 11 residue types from 5 crops and manure from 5 types of livestock were estimated. During the investigated period, gross biomass generated from crop residue was 11 and 13 t per smallholder household, of which 63% and 84% are estimated as surplus in KwaZulu-Natal and Limpopo, respectively. The gross biomass generated from animal manure was 158 and 84 t per smallholder household in KwaZulu-Natal and Limpopo, respectively, of which 48% are estimated as surplus. Estimated biomethane potential from the surplus crop residue is approximately 1370 Nm³CH₄ per year per smallholder household, equivalent to 49.3 GJ of heat energy. For methane, estimated potential from animal manure is 2105 and 1135 Nm³CH₄ per year per smallholder household, equivalent to 76 and 41 GJ of heat energy, for KwaZulu-Natal and Limpopo, respectively. The estimated energy potential is higher than low-income South African households’ cooking (19.8 GJ y⁻¹) and total (49.3 GJ y⁻¹) energy demand, theoretically enabling the complete substitution of current domestic fuels. The total estimated digestate from all residues contains approximately 0.32 t nitrogen, equivalent to 0.70 t urea fertilizer, per year per smallholder household. The analysis indicates that anaerobic digestion based on agricultural residues can make a significant contribution to meeting energy and fertilizer needs of smallholder farmers in KwaZulu-Natal and Limpopo.

本文评估了南非夸祖鲁-纳塔尔省和林波波省2017-2018年间小农耕作系统中可用于生产沼气的农业残余物。生物量估计是结合小农调查，公开数据和文献模型进行的，估计了5种农作物的11种残渣类型和5种牲畜的粪便。在调查期内，每个小农户的农作物残渣产生的总生物量分别为11吨和13吨，其中夸祖鲁-纳塔尔省和林波波省分别估计有63％和84％为过剩。在夸祖鲁-纳塔尔省和林波波省，每个小农户的动物粪便产生的总生物量分别为158吨和84吨，其中48％被估计为过剩。剩余农作物残渣估计的生物甲烷潜力约为1370 Nm每个小农户每年³ CH ₄，相当于49.3 GJ热能。对于甲烷，估计每个小农户每年从动物粪便中获得的潜力为2105和1135 Nm ³ CH ₄，相当于夸祖鲁-纳塔尔省和林波波省的热能分别为76和41 GJ。估计的能源潜力高于南非低收入家庭的烹饪（19.8 GJ y ^-1）和总计（49.3 GJ y ^-1）的能源需求，从理论上讲可以完全替代当前的家用燃料。每个小农户每年估计的所有残渣中的消化物总氮含量约为0.32吨，相当于0.70吨尿素肥料。分析表明，基于农业残留物的厌氧消化可为满足夸祖鲁-纳塔尔省和林波波省小农的能源和肥料需求做出重要贡献。