Jim Hammond

The feasibility and costs of biochar deployment in the UK

Biochar allows long-term (multi-centennial) soil carbon storage, with potential benefits for agricultural sustainability (e.g., productivity, reduced environmental impacts and water retention). Little is know about the costs of producing biochar and this study attempts to provide a ‘break-even selling point’ for biochar, accounting for costs from feedstock to soil application and revenues from electricity generation and gate fees. Depending on the assumptions used, biochar in the UK context may cost between GB£-148 t-1 and 389 t-1 (US

Pyrolysis biochar systems for recovering biodegradable materials: A life cycle carbon assessment

-222 to 584) produced, delivered and spread on fields, which is a provisional carbon abatement value of (GB£-144 tCO2–1 to 208 tCO2–1). A negative cost indicates a profit-making activity. The most profitable source of biochar is from wastes, but such materials will face complex regulatory issues and testing.

Competing uses for China's straw: the economic and carbon abatement potential of biochar

A life cycle assessment (LCA) focused on biochar and bioenergy generation was performed for three thermal treatment configurations (slow pyrolysis, fast pyrolysis and gasification). Ten UK biodegradable wastes or residues were considered as feedstocks in this study. Carbon (equivalent) abatement (CA) and electricity production indicators were calculated. Slow pyrolysis systems offer the best performance in terms of CA, with net results varying from 0.07 to 1.25tonnes of CO(2)eq.t(-1) of feedstock treated. On the other hand, gasification achieves the best electricity generation outputs, with results varying around 0.9MWhet(-1) of feedstock. Moreover, selection of a common waste treatment practice as the reference scenario in an LCA has to be undertaken carefully as this will have a key influence upon the CA performance of pyrolysis or gasification biochar systems (P/GBS). Results suggest that P/GBS could produce important environmental benefits in terms of CA, but several potential pollution issues arising from contaminants in the biochar have to be addressed before biochar and bioenergy production from biodegradable waste can become common practice.

Biochar field testing in the UK: outcomes and implications for use

China is under pressure to improve its agricultural productivity to keep up with the demands of a growing population with increasingly resource‐intensive diets. This productivity improvement must occur against a backdrop of carbon intensity reduction targets, and a highly fragmented, nutrient‐inefficient farming system. Moreover, the Chinese government increasingly recognizes the need to rationalize the management of the 800 million tonnes of agricultural crop straw that China produces each year, up to 40% of which is burned in‐field as a waste. Biochar produced from these residues and applied to land could contribute to Chinas agricultural productivity, resource use efficiency and carbon reduction goals. However competing uses for Chinas straw residues are rapidly emerging, particularly from bioenergy generation. Therefore it is important to understand the relative economic viability and carbon abatement potential of directing agricultural residues to biochar rather than bioenergy. Using cost‐benefit analysis (CBA) and life‐cycle analysis (LCA), this paper therefore compares the economic viability and carbon abatement potential of biochar production via pyrolysis, with that of bioenergy production via briquetting and gasification. Straw reincorporation and in‐field straw burning are used as baseline scenarios. We find that briquetting straw for heat energy is the most cost‐effective carbon abatement technology, requiring a subsidy of

Biochar in European Soils and Agriculture: Science and Practice

7 MgCO2e−1 abated. However Chinas current bioelectricity subsidy scheme makes gasification (NPV

The potential role of biochar in combating climate change in Scotland: an analysis of feedstocks, life cycle assessment and spatial dimensions

12.6 million) more financially attractive for investors than both briquetting (NPV

Biochar, Tool for Climate Change Mitigation and Soil Management

7.34 million), and pyrolysis (

Prospective life cycle carbon abatement for pyrolysis biochar systems in the UK

−1.84 million). The direct carbon abatement potential of pyrolysis (1.06 MgCO2e per odt straw) is also lower than that of briquetting (1.35 MgCO2e per odt straw) and gasification (1.16 MgCO2e per odt straw). However indirect carbon abatement processes arising from biochar application could significantly improve the carbon abatement potential of the pyrolysis scenario. Likewise, increasing the agronomic value of biochar is essential for the pyrolysis scenario to compete as an economically viable, cost‐effective mitigation technology.

An assessment of the benefits and issues associated with the application of biochar to soil

Background: There is a lack of biochar field trials in temperate climate regions. Wood biochar was applied during 2009–2011 to seven field experiments on five working farms in the UK, for arable, legume, horticultural and root crops. Results: Three trials showed no significant (p > 0.05) effect on crop yield, two showed positive effects of 5–6%, one showed a very strong increase of 100% and one showed a decrease of 2–16%. A meta-analysis of effect sizes was conducted for all treatments (n = 47), which showed a significant (p < 0.05) positive effect, increasing average yield by 0.4 t ha-1. Biochar application rates of 20 t ha-1 or under led to the greater benefits. Conclusion: This paper shows that, in some situations, biochar can bring benefits in modern temperate farming.

Maximizing the greenhouse gas reductions from biomass: The role of life cycle assessment

As demonstrated by several scientific studies there is no doubt that biochar in general is very recalcitrant compared to other organic matter additions and soil organic matter fractions and also that it is possible to sequester carbon at a climate change relevant time scale (~100 years or more) by soil application of biochar. However, the carbon stability of biochar in soil is strongly correlated with the degree of thermal alteration of the original feedstock (the lower the temperature, the larger the labile fraction) and in depth understanding of the technology used and its effect on the biochar quality is necessary in order to produce the most beneficial biochars for soil application. Beside carbon sequestration in soil biochar may improve the GHG balance by reducing N2O and CH4 soil emissions, although contrasting results are found in the literature. The mechanisms behind these reductions remain unclear and more research is required in order to investigate the various hypotheses in more detail, and to unravel the complex interaction between biochar, crop and soil, especially under field conditions. In conclusion, our current knowledge is largely based on short-term lab studies and pot experiments, which have provided detailed insight in certain processes and aspects of biochar application to soils, but suffer from large uncertainties when scaled-up to the farmers field level. In order to produce more realistic scenarios of the potential impact of biochar on C sequestration and soil GHG emissions there is a need to bring biochar research up to the field-scale, and to perform longer-term studies.