Biochar's cost constraints are overcome in small‐scale farming on tropical soils in lower‐income countries

Abstract

Biochar has been lauded for its potential to mitigate climate change, increase crop yields and reverse land degradation in tropical agricultural systems. Despite its benefits, confusion persists about whether the use of biochar is financially feasible as a soil ameliorant. A comprehensive review of previous studies of biochar's financial feasibility was performed (33 relevant publications). Financial performance appraisal (US$ Mg-1 biochar) and greenhouse gas abatement cost estimates (US$ Mg-1 CO2e) were used to gauge the financial feasibility of the biochar scenarios within each publication. Ordinary Least Squares Multiple Linear Regression was used to evaluate the predictive capacity of scenario financial feasibility as dependent on variables including national income levels, This article is protected by copyright. All rights reserved. climatic conditions, pyrolysis technology scales and pyrolysis capabilities. Analysis revealed that scenarios where biochar was applied targeting yield increases in high-value crops in tropical locations with low incomes and biochar-focused small-scale production, were overall significant predictors of biochar scenario financial feasibility. We find that the average abatement cost of biochar applied in 'lower-income countries' is-US$58 Mg-1 CO2e (financially feasible) compared with +US$93 Mg-1 CO2e in 'higher-income countries' (not financially feasible). Climate policies of lower-income countries in tropical climates should consider biochar as an input for small-scale climate smart agriculture to address land degradation in tropical agricultural systems. Based on recent evidence it is suggested that biochar fertilizers, a value-added biochar product, could present a commercially feasible pathway for biochar value-chain development in higher-income countries.

Deployment of Negative Emissions Technologies at the National Level: A Need for Holistic Feasibility Assessments

“…Assessing the feasibility of NETs can be described as a process, with different assessments of feasibility carried out at different moments in time. These range from specific assessments like technology-or dimension-focused (e.g., Fuss et al, 2018;Nemet et al, 2018;Roe et al, 2019;Robb et al, 2020), reviews or syntheses of multiple dimensions or comparison of NETs (Oschlies and Klepper, 2017;Minx et al, 2018;Waller et al, 2020), and combined feasibility assessments (IPCC, 2018). These assessments accordingly differ in scope and how feasibility is operationalized.…”

How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar

“…Higher rates (10–50 Mg ha −1 ) have commonly been applied where low‐nutrient biochar is used as a soil conditioner to improve bulk soil chemical and physical properties, while lower rates (<1 Mg ha −1 ) have been used as a nutrient carrier to increase fertilizer use efficiency and decrease nutrient losses, and in mechanized planting (Table S1). Economic analyses suggest that formulations combining biochar with fertilizer (biochar compound fertilizer [BCF]), applied at low rates, are likely to be the most cost‐effective approach for broadacre cropping in higher income countries (Robb et al, 2020).…”

Effects of Leucaena biochar addition on crop productivity in degraded tropical soils

“…However, for biochar to be an economically feasible and scalable solution, it must confer crop productivity benefits, be produced from feedstocks available locally and using low-cost, decentralized pyrolysis technologies [21]. We produced biochar from Leucaena using a lowcost retort kiln which, although offering limited control over pyrolysis conditions, is particularly suited for use in low and middle income countries and in smallholder farming systems as a shared community resource [39].…”

“…Despite the potential for biochar application on tropical soils, for its adoption by rural smallholder farmers in developing countries to be economically feasible, small-scale decentralised pyrolysis technology must be utilised with feedstocks obtained locally and a focus on higher-value (non-cereal) crop yield improvement [21,22]. We therefore tested whether a low-cost, locally produced biochar, using Leucaena leucocephala biomass, could elicit a crop yield response in Amaranthus across three degraded agricultural soils from Malaysia with low fertility and a range of soil pH.…”