The effect of pyrolysis temperature (T) and biomass particle size (z) on the biocoal's heating value of Oak acorn shell (OA), deseeded carob pods (CP) and olive mill solid waste (OMSW) were investigated. The higher heating value (HHV) increased with T. The effect of the particle size differed according to the biomass. Response surface methodology (RSM) was used to optimise the biocoal production system from technical, end-user and socio-environmental perspectives. The maximum HHV, representing the technical objective, is achieved at maximum T and minimum z for OA biocoal; at maximum T and minimum z for OMSW and at maximum T and maximum z for CP. The highest lower heating value (LHV), corresponding to end-user, for OA biocoal is achieved when T is greater than 450 °C and z < 1000 μm. For OMSW, particle size was the most important factor with the best LHV achieved when z > 1750 μm. The maximum net energy return per kg of biomass processed and maximum GHG offset (socio-economic) is realised at the lowest T for all biomass and particle sizes. This study is relevant to policy makers as it highlights potential conflict between the optimal conditions to produce high quality biocoal characterised by its high LHV and the optimal conditions to achieve the maximum utility from the resource and in turn potentially higher socio-environmental return.

研究了热解温度 (T) 和生物质粒径 (z) 对橡子壳 (OA)、去籽角豆荚 (CP) 和橄榄磨固体废物 (OMSW) 的生物煤热值的影响。较高的热值 (HHV) 随 T 增加。颗粒大小的影响因生物质而异。响应面方法 (RSM) 用于从技术、最终用户和社会环境角度优化生物煤生产系统。代表技术目标的最大 HHV 是在 OA 生物煤的最大 T 和最小 z 时实现的；OMSW 最大 T 和最小 z，CP 最大 T 和最大 z。当 T 大于 450 °C 且 z < 1000 μm 时，OA 生物煤的最高低热值 (LHV) 对应于最终用户。对于 OMSW，粒径是最重要的因素，当 z > 1750 μm 时达到最佳 LHV。对于所有生物质和颗粒尺寸，每公斤生物质加工的最大净能量回报和最大温室气体抵消（社会经济）在最低 T 下实现。这项研究与政策制定者相关，因为它强调了生产以高 LHV 为特征的高质量生物煤的最佳条件与实现资源最大效用的最佳条件之间的潜在冲突，进而可能带来更高的社会环境回报。