Indigenous peoples created one of the most effective technologies to counter global warming, and yet the industrialised world still largely ignores it. What has gone wrong with how we understand, value and apply technology?
In the late 19th century, European explorers in the Amazonia found large areas of dark, high fertility soils amidst the region’s highly weathered, thin and acidic soils. These soils were termed terra preta (dark soils). They were likely developed by indigenous people who dumped near their settlements food scraps, manure and sewerage waste, ashes and charcoal. Over decades these dumps matured into highly productive anthropogenic soil oases within tropical soil deserts.
The biochar-based terra preta soils likely began accidentally, and then through trial and error were improved and extended in area as indigenous people saw the productivity benefits.
Terra preta soils are believed to take around forty or fifty years to form. They date back over a thousand years. They can be two metres deep. Terra preta soil appears to regenerate itself at the rate of around one centimeter per year.
These carbon-rich soils foster microbial activity that improves nutrient availability and plant growth. They typically double crop production compared to adjacent, non-biochar enriched soils, and they do so without exhausting soil fertility.
Indigenous peoples in Ghana and Liberia have also used biochar to turn highly weathered, nutrient-poor tropical soils into enduringly fertile, carbon-rich black soils. Researchers from universities such as Cornell and the University of Sussex have lived and worked within these communities to learn how they created these “African Dark Earths”.
Pre-European Māori modified soils with sand and gravel to improve drainage. Charcoal might have been introduced to hold moisture and to help warm the soil. Rigg & Bruce (1923) report charcoal in Waimea West soils. Charcoal associated with Māori settlements has been dated as early as around 700 years ago (Calvelo Pereira et al 2014).
However, terra preta-type dark soils akin to those in the Amazonia and West Africa were not developed in New Zealand. This may partly be because Māori had strong cultural objections to using wastes such as manure in gardening. As part of their “recipe”, terra preta soils require such waste inputs as well as charcoal.
However, biochar is now an integral part of the farming operations of Pārengarenga Incorporation, an iwi-owned enterprise in the Far North. It transforms waste forest slash into biochar, which is then used for example as a cattle feed animal health supplement, until finally the biochar ends up in the soil as enriched manure. This has proved profitable through pasture improvements and enhanced animal health lifting productivity.
Only in recent times has the importance of carbon in soil been recognised for its wider climate change mitigation and environmental benefits. Soils contain more carbon than both terrestrial plants and the atmosphere combined. However, since agriculture began around 12,000 years ago about 133 billion tonnes of carbon have been lost from soil. Every tonne of carbon lost from soils adds 3.67 tonnes of carbon dioxide to the atmosphere.
A top priority in climate change mitigation is reducing carbon dioxide and other greenhouse gas emissions. However, to avoid a catastrophic climate change tipping point, negative emissions technologies that sequester carbon in soil are needed. We must therefore stop mining soil carbon and instead use biochar to restore carbon in soils by sucking carbon dioxide out of the atmosphere.
Most soil carbon is labile, that is as biomass decomposes it re-emits carbon dioxide back into the atmosphere as part of the fast carbon cycle. In contrast, pyrolysis that turns biomass into biochar converts fast cycle carbon into slow cycle carbon, which is effectively permanent carbon sequestration.
Biochar is not soil or fertiliser. It is carbon with high porosity, high surface area and Cation Exchange Capacity (CEC). Porosity means biochar stores and recycles water, which is beneficial in arid soils. Porosity and CEC helps nutrient retention and recycling, and is associated with enhanced microbial activity and with healthier and more diverse soil microbiome.
Biochar is 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 catalyse at other times. It can reduce methane and nitrous oxide emissions and reduce nitrate pollution in water. It can be used to purify wastewater. It can remediate contaminated soils. It can enhance compost’s effectiveness.
Biochar can enhance the functionality and lifecycle environmental benefits of construction, food packaging and storage materials. It can be used to make high-tech products such as super-capacitators. It can be used for activated carbon, carbon black, in paints, medicines, and as a decontaminant in biogas production. Above all, biochar can sequester carbon over intergenerational time frames.
As well as its productivity benefits, biochar could become the world’s single most important negative carbon emissions technology, and New Zealand is well-placed to lead on this because of our available biomass. Given this, how can we explain why biochar has not been developed and applied widely?
Biomass is a very diffuse resource and expensive to transport. It is difficult to achieve scale economies. Biochar needs to be produced and applied locally and on a relatively small scale. “One size does not fit all” with biochar. To be effective, a biochar production regime must match a specific biomass source and pyrolysis setting to value-add cascades and to the final biochar end use.
Governments respond to concentrated lobbies, not individuals or small communities working in isolation. Technocrats seek centralised solutions to complex problems that in fact require a decentralised and circular economy response.
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 it cannot be monopolised by a few large and politically influential companies.
Existing industries defend their financial interests by “buying science”. The science peer review process can entrench specialised disciplinary silos. Many scientists struggle to work across disciplines. Soil scientists and agronomists have delivered great biochar research, however this has not always been well connected to other fields such as climate and atmosphere science, animal health research, material science, and to climate change policy making.
Biochar sits uncomfortably with orthodox economic theory and tools. It is best suited to the circular economy model. Biochar might be seen as an expenditure on an input when it is really an investment in an enduring productive capital asset. Rather than depreciate, biochar endures in soil and its functionality can improve over time. Kelpie Wilson suggests biochar is like an aged cheese where the quality is easy to recognise but the exact recipe and the effects of time have yet to be understood scientifically. Biochar may be costly to apply initially, however once in the soil it enhances productivity over intergenerational timeframes.
Biochar can be used for a wide range of economic purposes and then be stored in the soil as a permanent carbon store. This effectively involves “value-add cascades”. 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 purposes such as removing nutrients from waste streams that would otherwise pollute waterways. The resulting nutrient-enriched biochar then “value-add cascades” down to its next use in lifting soil productivity through fertilisation and enhanced nutrient recycling. The final value-add cascade for this biochar is its inter-generational presence as a permanent carbon store in the soil.
A way forward with biochar might be to work with Māori and other partners to apply it in local farms, orchards and forests as part of an inter-generational kaitiakitanga ethos and kaupapa. This could be customised around the specific soil and productive conditions, the intended final uses, and the value-add cascades that lead up to this.
Grimes et al (2015) reported that Māori placed more priority on environmental protection than non-Māori New Zealanders. Inalienable Māori land cannot be sold and therefore it cannot be “farmed” for capital gains. This forces the focus to be on intergenerational sustainable production.
Whilst the legal ownership structure and the Māori sustainability ethos support biochar initiatives, biochar production regimes are highly differentiated depending on local factors such as soil types, biomass sources and desired value-add cascades and end uses. Applied research, including pilot projects are therefore needed.
Integrated technical, economic and environmental assessments and pilot projects could be undertaken on different opportunities. This might involve sectors such as dairy, sheep and beef, wine, kiwifruit, apples and field crops. It might also focus on particular soil types such as low fertility, arid or poorly drained soils. Biochar could be trialled as a compost additive and in animal health and bioremediation applications. Different biomass sources such as willows, forest residues and biomass waste streams could also be evaluated for their value for biochar.
Biochar initiatives with Māori and other partners would deliver results that can be applied more widely, and work towards global commons and intergenerational benefits. Because Māori cannot fully capture the benefits of these investments there is a strong case for public funding or co-funding. This should be invested in research and applied technology in support of Māori leading on their own lands, and in accord with kaitiakitanga and the supporting sustainable development kaupapa.
Calvelo Pereira; R. Camps Arbestain, M. et al 2014: Detailed carbon chemistry in charcoals from pre-European Māori gardens of New Zealand as a tool for understanding biochar stability in soils. European Journal of Soil Science, January 2014, 65, 83–95.
Grimes, A. et al 2015: Indigenous Belief in a Just World. NZ Māori and other ethnicities compared. Motu Economic and Public Policy Research.
Rigg, T.; Bruce, J. 1923: The Maori Gravel Soil of Waimea West, Nelson, New Zealand. Journal of the Polynesian Society 32: 84 – 93.