Soil Sharing: Terra Preta, Biochar and early Bio-economies

words Ibrahim Kombarji

What and how biochar has become a solution and economical market and what does it mean for us and the upcoming generations?

Biochar: a system rather than only a material

During the past twenty years, Dr. Johannes Lehmann has focused on «nano-scale investigations of soil organic matter, the biogeochemistry of pyrogenic carbon in soil and sustainable land use». Dr. Lehmann is a professor of soil fertility management and soil biogeochemistry at Cornell University, New York. Lehmann looks at the forms of organic carbon and nutrients that are important in the «stabilization and global cycles that inform approaches to climate mitigation and circular economy».

Lehmann explains biochar as «the product of heating biomass in the absence of or with limited air to above 250ºC, a process called charring or pyrolysis also used for making charcoal. The material distinguishes itself from charcoal or other carbon (C) products in that it is intended for use as a soil application or broader for environmental management». He continued by highlighting that in some instances, the material properties of biochar may overlap with those of charcoal as an energy carrier, but many types of biochar do not easily burn and charcoals are typically not made to address soil issues.

Dr. Johannes Lehmann: defining biochar

Lehmann stressed that a defining feature of biochar, similar to charcoal, is «a certain level of organic C forms, called fused aromatic ring structures». In this definition it is to note that biochar is a system rather than only a material. Dr. Lehmann introduced the early works of Dutch soil scientist Wim Sombroek as a core layer in our understanding of soils and biochar today.

Sombroek mentioned using «technology that produced terra preta in the 1960s» as Lehmann clarified. Today, the term «Amazonian dark earths-Terra Preta de Índio» refers to «a dark soil most often found in limited zones in the lowland areas of Amazonia. These soils are, as a rule, concentrated near rivers and located on bluff zones above the floodplains. These soils are characterized by a long-term fertility» (Klaus Hilbert and Jens Soentgen).

This unique soil type has a «higher nutrient content, especially phosphorus and nitrogen, and a much higher pH value when compared to other Amazonian soils» (Hilbert, Soentgen). The «large-scale production» of this very dark soil is «said to be an effective tool in efforts to mitigate global warming». According to Denevan and Woods, the Terra Preta sites cover «an area of 0.1–0.3% (6000–18,000 km2) of the wooded Amazonian lowlands».

2021 COP26: soil as the next frontier for storing carbon

Later this year, the city of Glasgow will host the COP26. This international conference reunites over 190 countries around one same purpose which is to «control the increase in greenhouse gases caused by man, with the aim of avoiding a dangerous disruption of the climate». Every year, in anticipation of this constant «last hope» event, world leaders from across the globe express the underlying urges and possible outcomes around this summit.

We are starting to hear the expectations of some, such as Angela Merkel, who «hopes this summit will give new impetus to concrete measures». Others such as Joe Biden have set greenhouse emission targets and expressed his interest in looking at the soil as «the next frontier for storing carbon» in light of the COP26. Soil as a carbon mitigation strategy will be a highlight of this year’s summit. New world climate policies involving biochar and other similar approaches can be implemented soon in another interminable effort to address the climate crisis. How did biochar develop as a solution and what are its potential usage?

Lampoon reporting: biochar as one option to manage soil organic carbon

Until 1992, this soil was studied within the context of ethnological, historical and archeological data. Sombroek’s «vision» was to study this soil «infused with climatic sciences and concerns». He did this through concentrating the scientific efforts to «manufacture Terra Preta Nova through the introduction of plant charcoal to nutrient-poor soils». Almost thirty years later, the Terra Preta Nova, as a concept and a physical substance, has now been seized up by commercial interests and its being offered on the home improvement and horticultural market right alongside the more widely known «enhanced home gardening soils» (Hilbert, Soentgen).

Lehmann explained that Sombroek «did not know that terra preta contains biochar. It is then a few years later that the notion of biochar systems as a net carbon negative energy came in the mid-2000s through budding conversations between engineers, soil scientists and archaeologists». This anecdote around this black earth as «a climate savior» reveals the advancements of science in adopting multi-disciplinary approaches that bring the efforts of different fields and visions to better understand a layer of our shared world soil.

The process to produce biochar

This approach perhaps has not occurred at the same time as the U.N.’s Rio de Janeiro Earth Summit in June of 1992. Lehmann’s interest in studying biochar also intersects with this anecdote. He was working on improving degraded soils in the central Amazon in 1997-2000, and he was intrigued by the terra preta soils. He started adding biochar to soil in 1999 «to investigate its effects». The process to produce biochar is «always the same, but the conditions such as temperature, pressure materialize to pyrolyze may vary».

Lehmann expressed the importance of biochar as one option to manage soil organic carbon. He explained «organic carbon contributes to many soil health functions. Soil organic matter is the central manageable property that controls soil health. Organic carbon in the form of biochar is always 1-2 orders of magnitudes more persistent than the organic matter it is made from. Some nutrients in residues becomes more, some nutrients less available to plants, when those residues are pyrolyzed».

Biochar to help decarbonize the fashion industry

Kathreen Draper, the US Director of the Ithaka Institute for Carbon Intelligence, which is «a non-profit research foundation and an open source-network for carbon strategies», explained that in Europe, the demand for biochar is «currently higher than supply which is not (yet) the case in the US and other parts of the world. There are a growing number of small to medium size vendors, with many more coming on line». Draper introduced new realities in the making highlighting the way biochar «can help decarbonize the fashion industry overall».

She introduced a few projects some «looking at converting post-consumer textile waste into biochar as an organics management process». Others are «exploring the use of biochar in textiles including masks, using biochar to sorb dyes in wastewater and using biochar on cotton fields that have been subjected to various chemicals for decades».

The price of biochar

It is still quite unclear to have a precise price for biochar, Draper reinforces that it is «highly dependent on the quality and consistency of the biochar and what market you are selling into as well as what products you are displacing. Some companies are selling for top dollar but only in small quantities to the horticulture market (price is likely to fall as production increases), whereas others are producing a low grade biochar from heterogenous waste streams and having a hard time finding large scale off-take agreements».

The advancement of the research and implementation of biochar has opened up a multiplicity of new research and potential solutions and hemp based biochar are currently being studied. In an effort to reduce increased carbon emissions, more attention is being given to the «circular bioeconomy» concept, which focuses on the sustainable re-use and valorization of waste biomass to increase their useful «service» life.

Bringing forward the potential of hydrochar

Nazih Kassem, a doctoral student at Cornell who works on techno-economic and life cycle modeling of integrated bio-energy systems is currently investigating the economics of using hydrochar as a soil amendment product versus an energy carrier. He explains «both biochar and hydrochar are produced from biomass. Unlike biochar, hydrochar is produced using hydrothermal processing in a water medium at high operating pressures and temperatures. This makes hydrothermal processing attractive for wet biomasses as it eliminates the need to dry the biomass feedstock before processing, which can be energy intensive. The different physiochemical characteristics of biochar and hydrochar implies different end-uses for each. Hydrothermal processing research is relatively new, and hydrochar properties are still being investigated to understand its full potential».

Using lignocellulosic biomass such as woody biomass and agricultural residues

Kassem brings forward the potential of hydrochar, «substituting coal with hydrocar can reduce the Carbon footprint of energy generation». He reinforced, using lignocellulosic biomass such as woody biomass and agricultural residues to produce biochar is one such example, where by-products of farming activities, which have limited to no economic value, are processed to higher-value soil amendment products. Other waste biomass wastes, such as animal manures, food wastes and sewage sludge, characterized by high moisture content, can also be thermochemically processed to produce hydrochar.

Kassem highlighted that hydrochar is valued (and therefore priced) differently for each end-use. This has implications on the financial profitability of biorefinery systems processing waste biomass. In his recent co-authored paper The concept and future prospects of soil health, Dr. Lehmann and his colleagues highlight the potential of Soil health «which is the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals and humans, and connects agricultural and soil science to policy, stakeholder needs and sustainable supply chain management».

This is an intricate starting point for many different fields, to better understand our relation to other microorganisms, elements, to understand that we are as humans part of larger atmospheres and ecosystems. Dr. Lehmann highlighted that the «soil health approach is a clear expansion beyond humans». As Dr. Lehmann highlights it, policy is important to make meaningful and large scale impact using biochar. These research practices and trials of scientists will feed on the discussion tables of decision makers at the Glasgow summit later this year, in hope that the implementation and research of biochar and other mitigation strategies will be reinforced post-COP26.