Biochar is an effective negative emissions technology: so what are we waiting for?

The IPCC notes that even massive reductions in carbon emissions will be inadequate to achieve carbon neutrality by 2050.  It states that “there is additional need for large-scale atmospheric carbon dioxide removal (CDR) to prevent overshooting the 1.5°C temperature threshold”.  Given that soils contain more carbon than both terrestrial plants and the atmosphere combined, it is therefore surprising there is so little focus placed on biochar as a carbon sink.

The October 2018 IPCC special report highlighted Pyrolytic Carbon Capture and Storage (PyCCS), that is biochar, as a promising negative emission technology (NET).  Natural biological processes break down biomass and soil carbon releasing carbon dioxide into the atmosphere.  Biochar differs because it is a stable carbon form that is retained in the soil for the long term. PyCCS can therefore be a core NET to solve humanity’s great existential threat – climate change.


What is biochar?

Pyrolysis turns biomass into charcoal (biochar) and also produces biogas and bio-oil by-products.  The biochar is added to soil to improve productivity and store carbon for the long-term.

Charcoal is often found in soils, made by grassland and forest fires and retained over millennia.  This natural biochar is at high levels in some of the world’s most valuable agricultural soils: the Russian Chernozem and the US Mollisols. However, intensive agricultural practices and deforestation have effectively mined carbon from many of the world’s soils, and modern industrial agriculture has become heavily dependent on synthetic fertiliser inputs.

Using charcoal in soils is an ancient technology used to restore carbon and to lift agricultural productivity.  In tropical soils plant material rapidly breaks down and releases carbon into the atmosphere.  Amidst low fertility Amazonian oxisol soils, indigenous people created rich Terra Preta soils over centuries.  These soils began as dumps of food scraps, manure and sewerage waste, ashes and charcoal.  Over decades these dumps matured into highly productive soil oases within tropical soil deserts.

Asian countries have a long history of using biochar in soil.  Rice husk biochar has been used since the beginning of rice cultivation in Asia.  Biochar is used in Europe and Asia as a feed ingredient for animal health purposes and to lift animal productivity, with the biochar then returned to the soil through manure and other waste.

What is biochar used for?

Biochar’s surface area, porosity, conductivity and other characteristics make it a general purpose substance with multi-purpose functionality in diverse applications.  It can remove pollutants and yet retain water.  It can help recycle nutrients and upcycle waste.  It can immobilize at times and catalyze at other times.

Biochar production technologies can convert agricultural, horticultural, vineyard, municipal and other waste into something valuable.  Biochar can reduce nutrient loss, improve nutrient recycling, increase soil life and enhance soil productivity.   It can reduce nitrous oxide emissions and reduce nitrate pollution in water.  It can enhance compost’s effectiveness. It can be used to purify waste water.  It can remediate contaminated soils.  It can enhance the functionality and lifecycle environmental benefits of construction, food packaging and storage materials.  It can be used as an animal feed additive, colouring agent, and as a low cost and more sustainable material for activated carbon. It can also be used in carbon black, in paints, medicines and as a decontaminant in biogas production. Above all, biochar can sequester carbon over the very long term.

Why is biochar not promoted as a core negative emissions and sustainability technology?

Biochar is one of the most important technologies we have to counter anthropogenic global warming and contribute to sustainability.  Given this, how can we explain why biochar has not been developed and applied widely?

Governments respond to concentrated lobbies, not individuals working in isolation.  Technocrats seek centralised solutions to complex problems that in fact require a society-wide and decentralised response. Fund technology to refreeze the North Pole!  Ocean iron fertilisation!  Stratospheric sulfate aerosols!  Deflecting solar radiation with space-based sunshade mirrors!  Such technological interventions come from those who presumptuously assume they can act for the planet without an inclusive mandate to do so.  Such technological fixes are unlikely to be acceptable even if they were practical.  They would inevitably come with unexpected environmental downsides.

As with distributed electricity generation, biochar technology would decentralise economic power away from the cities and to the regions. Biochar can be a tool for hundreds of thousands of individuals, communities, cooperatives, farmers, horticulturalists and small holders and cannot be monopolised by a few large companies.

Vested industries defend their financial interests by “buying science”. The science peer review process entrenches specialised disciplinary silos.  Few scientists can work across disciplines. Soil scientists and agronomists have bravely driven biochar research, however this has not been well connected to other fields such as climate and atmosphere science, animal health research, material science, and above all to climate change policy making.  Although tens of thousands of pyrolysis and biochar papers have been published, few are linked to climate change science that is core to IPCC reports and they are therefore not integrated into climate change policy responses.

Politicians and officials focus on attempts to create enforceable international agreements based on market trade principles.  For emissions markets to function effectively, the units have to be measurable, the train of transactions visible, and the trading rules enforceable.  Climate change mitigation rules can favour what is measurable at the expense of what can be most effective.  Soil carbon can be measured, however is difficult to predict with precision how long a specific biochar product will store carbon in a particular soil.  Likewise, it is difficult to predict carbon’s likely storage life in solid wood products.

How does biochar compare with other Negative Emissions Technologies?

Direct Air Capture with Carbon Storage (DACCS) and Enhanced Weathering have yet to be proven scalable, will be costly, produce no spin-off benefits, and may come with environmental risks and other unintended consequences.  Planting trees sequesters carbon, but only while the trees are growing.  If retained as a permanent forest the amount of carbon trees sequester is eventually capped.  If trees are harvested, some carbon is sequestered in long-life wood products such as housing, however most is lost.  Non-biochar soil organic matter can be enhanced through different agronomic and other techniques, however these have limits beyond which soils are saturated, and some techniques can reduce productivity.

In contrast, biochar can be used for a wide range of economic purposes and then be stored in the soil as a long-term carbon store.  This effectively involves “cascading uses”.  For example, making biochar produces some process heat and bio-oil that can be used for example in industrial processes.  The biochar can then be used for many different purposes such as waste treatment.  The nutrient-enriched biochar resulting from its waste treatment use then cascades down to its next use in lifting soil productivity through fertilisation and enhanced nutrient recycling to reduce nutrient loss.  The final cascading use for this biochar is its long-term presence in the soil.

What we should do to make biochar happen in New Zealand?

Biochar could become the world’s single most important negative carbon emissions technology.  New Zealand is well placed to lead in biochar because we are a biologically-based economy and biochar can target our key environmental challenges.  These include biochar reducing nitrous oxide emissions from pastoral farming, reducing nutrient loss, and building up soil carbon stores to offset emissions.  Pyrolysis can turn forestry, horticulture and intensive animal industry waste streams into valuable products.

To make biochar happen in New Zealand we need to recognise it in our international climate change commitments as a NET.  We need a Certification scheme to ensure the right biomass is turned into biochar and matched to the right uses and that it is sequestered in the right soils.  This could be based on the European Biochar Certificate that ensures safe, sustainable and fit for purpose biochar production and use through the lifecycle.

We need New Zealand-specific research to match biochar from specific biomass products to particular soil environments for specific productive purposes. This research must translate into technology that is applied in productive systems.

In future posts I will address these research and technological opportunities in the context of specific New Zealand industries.

About Peter Winsley

I’ve worked in policy and economics-related fields in New Zealand for many years. With qualifications and publications in economics, management and literature, I take a multidisciplinary perspective to how people’s lives can be enhanced. I love nature, literature, music, tramping, boating and my family.
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5 Responses to Biochar is an effective negative emissions technology: so what are we waiting for?

  1. David Lillis says:

    Another excellent piece, and a timely reminder of your work on biochar around 2007. The science on biochar is compelling and it is a pity that few in the climate change community around the world (IPCC, policy-makers at governmental and regional levels, researchers, political leaders etc) have taken note of the potential to mitigate carbon significantly. Perhaps there is the possibility that New Zealand can develop a biochar industry, but someone must advocate and the New Zealand climate change community has to listen.

    Unfortunately, none so blind as he who will not see nor so deaf as he who will not listen! The recently-released series on the Chernobyl disaster of 1986 illustrates the problem – political leaders who had no scientific training not listening (at least initially) to the concerns of nuclear physicists and engineers who were warning of the scale of the problem within hours of the accident.

    Who can advocate for biochar?


    • trlahh says:

      Hi David,
      “Who can advocate for biochar?” …. that is one of the tasks we have set ourselves at Biochar Network NZ (BNNZ It is a new organisation, and the website is still being fleshed out. A lot of historic data on biochar in NZ can be found at the related site AllBlackEarth ( and the associated FB page.

      BNNZ is busy on the policy front, trying to engage with industry and govt. But we have few resources and need help, so we welcome this new article from Peter and look forward to much more debate on the subject of biochar in NZ.
      Trevor Richards,
      BNNZ secretary

      • Frank Strie - Terra Preta Developments says:

        Yes Trevor, I fully support your comments. Over here in Tasmania it has been a very long and lonely time for freelancers like us ( ) , The official researchers were telling me for some years now:” No budget funding = no work and no serious interest on investigating Biochar. So what option was left?
        Just get on with what we know needs doing and work towards it with world wide willing and likeminded collaborators such as yourself and the Fachverband Pflanzenkohle in Germany, Austria & Switzerland.
        Interesting times
        Frank – producer, user and trader of
        FRANK’S CHAR Tasmania

  2. David Lillis says:

    Peter, Trevor and Frank.

    I was not aware of biochar groups such as yours. Very pleasing to see that you are active in the promotion and dissemination of knowledge about biochar. Good luck!


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