Small-scale biochar production on Swedish farms: A model for estimating potential, variability, and environmental performance

Elias S Azzi,Erik Karltun,Cecilia Sundberg

doi:10.1016/j.jclepro.2020.124873

Abstract

Several small-scale pyrolysis plants have been installed on Swedish farms and uptake is increasing in the Nordic countries. Pyrolysis plants convert biomass to biochar for agricultural applications and syngas for heating applications. These projects are driven by ambitions of achieving carbon dioxide removal, reducing environmental impacts, and improving farm finances and resilience. Before policy support for on-farm pyrolysis projects is implemented, a comprehensive environmental evaluation of these systems is needed. Here, a model was developed to jointly: (i) simulate operation of on-farm energy systems equipped with pyrolysis units; (ii) estimate biochar production potential and its variability under different energy demand situations and designs; and (iii) calculate life cycle environmental impacts. The model was applied to a case study farm in Sweden. The farm’s heating system achieved net carbon dioxide removal through biochar carbon sequestration, but increased its impact in several other environmental categories, mainly due to increased biomass throughput. Proper dimensioning of heat-constrained systems is key to ensure optimal biochar production, as biochar production potential of the case farm was reduced under expected climate change in Sweden. To improve the environmental footprint of future biochar systems, it is crucial that expected co-benefits from biochar use in agriculture are realised. The model developed here is available for application to other cases.

Highlights

By managing land, humans produce biomass resources that provide food, materials, and energy services
To bridge the current knowledge gaps on pyrolysis operation and the limitations of static life cycle assessment (LCA) models, this study examined inclusion of energy system models in LCA
A unit commitment model (Atabay, 2017) was coupled with the LCA software brightway2 (Mutel, 2017) in order to: (i) simulate operation of on-farm energy systems equipped with pyrolysis units; (ii) estimate biochar production potential and its variability under different energy demand situations, including future climate; and (iii) generate detailed life cycle inventories of farm energy systems, to evaluate their environmental performance

Summary

Introduction

Humans produce biomass resources that provide food, materials, and energy services. Land use changes have emitted around one-third of cumulative anthropogenic carbon emissions, while fossil fuel combustion has emitted the remaining two-thirds (Berndes et al, 2012). Agricultural practices have been significant drivers of biodiversity loss and environmental degradation. Enabling farmers worldwide to reduce the environmental footprint of land use, while maintaining and increasing biomass production, is a long recognised challenge (Vasquez et al, 2018). If humanity fails to cut its greenhouse gas emissions sufficiently fast, the internationally agreed climate goals will require deployment of carbon dioxide removal (CDR) technologies (IPCC, 2018). Farmers can potentially contribute to CDR through their farming practices and energy systems

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