Biochar from cookstoves reduces greenhouse gas emissions from smallholder farms in Africa

Cecilia Sundberg,Gert Nyberg,Thomas Kätterer,James K Gitau,Petra Sieber,Geoffrey M Kimutai,Yahia Mahmoud,Dries Roobroeck,Kristina Roing De Nowina,Mary Njenga,Erik Karltun

doi:10.1007/s11027-020-09920-7

Abstract

Biochar produced in cookstoves has the potential to contribute to negative carbon emissions through sequestration of biomass carbon while also providing other benefits for sustainable development, including provision of clean renewable energy and increased yields in tropical agriculture. The aim of the reported research was to estimate effects on food production, household energy access and life cycle climate impact from introduction of biochar-producing cookstoves on smallholder farms in Kenya. Participatory research on biochar production and use was undertaken with 150 Kenyan smallholder farming households. Gasifier cookstove functionality, fuel efficiency and emissions were measured, as well as biochar effects on agricultural yields after application to soil. Cookstoves provided benefits through reduced smoke, fuel wood savings and char production, but challenges were found related to labour for fuel preparation, lighting and refilling. On-farm trials with varying rates of biochar inputs, in combination with and without mineral fertilizers, have led to a sustained increase of maize yields following one-time application. The climate impact in a life cycle perspective was considerably lower for the system with cookstove production of biochar and use of biochar in agriculture than for current cooking practices. Climate benefits from biochar production and use are thus possible on smallholder farms in sub-Saharan Africa, through reduced use of biomass in cooking, reduced emissions of products of incomplete combustion and sequestration of stable biochar carbon in soils. Biochar-producing cookstoves can be implemented as a climate change mitigation method in rural sub-Saharan Africa. Successful implementation will require changes in cooking systems including fuel supply, as well as farming systems, which, in turn, requires an understanding of local socio-cultural conditions, including power relations and gender aspects.

Highlights

In sub-Saharan Africa (SSA), high rates of deforestation (Leblois et al 2017) and soil fertility degradation (Le et al 2016) contribute profoundly to climate change and food insecurity
We provide here an overview of how the cooking and cultivation systems are affected by biochar introduction
The first version of the gasifier domestic cooking system saved 20–43% of fuel depending on fuel type and calculation method and reduced cooking time by 18% when using the same woodfuel (Njenga et al 2016)

Summary

Introduction

In sub-Saharan Africa (SSA), high rates of deforestation (Leblois et al 2017) and soil fertility degradation (Le et al 2016) contribute profoundly to climate change and food insecurity. Most households in SSA use wood, charcoal and/or crop residues as cooking fuels (Bonjour et al 2013), hanging on to traditional open combustion systems that have low energy efficiency and produce high emissions of health-affecting gases and fine particles (Jetter et al 2012). Stoves that pyrolyse biomass to produce heat for cooking and biochar for soil fertility improvement could be such an opportunity (Njenga et al 2016; Whitman et al 2011). Biochar can be produced from locally available biomass This is an opportunity as well as a risk, considering that biomass is a renewable but limited resource with various uses. Char-producing pyrolytic cookstoves could potentially produce biochar from local biomass resources already being used for cooking, reducing, rather than increasing, biomass demand (Njenga et al 2016). We provide here an overview of how the cooking and cultivation systems are affected by biochar introduction

Results

Discussion

Conclusion