Biochar for productivity and climate change mitigation: What are we waiting for?

If you wanted to invent a country best placed to manage climate change it would look a lot like New Zealand.  An island nation in the middle of a vast ocean, since oceans take the rough edges off some climate change extremes.  Mountainous, with abundant water, hydropower resources and geothermal power.  A high coastline to land area ratio and in the “Roaring Forties”, assuring high wind power capability.  Low cost, high carbon wood to underpin new sustainable development opportunities.

Yet the reality of human-induced climate change is still contested in New Zealand. Those who understand the hard science often struggle to keep track of the political-economy issues domestically and internationally.  Rhetoric, virtue signaling, and unfunded statements of wishful intent are often assumed to be binding treaty obligations and enforceable contractual law. 

Weaknesses in our climate change policies result from inconsistencies between the ETS system, emissions budgets, the “Nationally-Determined Contribution” (NDC) mechanism under the Paris Agreement, and the goal to achieve zero net emissions of greenhouse gases (with the exception of biogenic methane) by 2050.

The ETS mechanism seeks to use competitive pricing to internalize externalities through a market auction system.  In practice the ETS system has largely failed. The four New Zealand auctions held in 2023 did not get a single buyer. The March 2024 auction sold only $190M units to 16 participants, far less than expectations.

In December 2015, the Paris Agreement asked countries to declare an “Initial Nationally-Determined Contribution” (INDC) for the period 2021-30.  According to Barry Brill’s analysis the Ardern Government in 2021 offered to “donate” $30 billion for offshore climate change mitigation endeavours.  This was as part of its 2021-30 NDC under the Paris Agreement.  Offshore spending on such a scale and lacking rigorous investment analysis is surely a poor investment for New Zealand. There has been fraud as well as weak financial management in offshore carbon credit and offsets markets, lack of transparency and good accounting practice, and wild price swings.  Large sums of money have been spent with little to show for it.

Surely the 2050 goal could be achieved if NDC money was spent entirely in New Zealand, for example on offshore wind turbines, transportation electrification, passive energy housing, and in demonstrating how wood can replace oil, coal, natural gas, concrete and steel in energy, construction and other markets.

We should encourage foreign businesses to invest in New Zealand to replace their emission-intensive processes with the low or nil emission hydro, wind and geothermal energy we are endowed with. The Bluff aluminum smelter is a long-standing exemplar of such a strategy, and data centres could be part of our future.

The NDC is set at a more ambitious level than emissions budgets. Though policy papers refer to international “obligations” in relation to climate change, they are more lists of what the government expects to do voluntarily, with no treaties, contracts, or enforcement mechanisms and no rigorous Parliamentary Budget assessment process standing behind them.   

The Paris Agreement specifically supports addressing climate change “in a manner that does not threaten food production.” The food and fibre sector dominates New Zealand’s economy.  It accounts for around 80% of New Zealand’s merchandise exports – $57.4 billion in the year to 30 June 2023.  Yet our pastoral farmers are treated derisively despite being among the best educated farmers in the world, running pastoral industries and supply chains that are world leaders in energy efficiency and low carbon use.

New Zealand climate policy has focused markedly on methane, though our emissions have remained quite stable for the last twenty years, and methane breaks down more quickly than CO₂.  From at least 1991 the global warming potential (GWP) of ruminant methane was believed to be 28 times more than CO₂.  However, from 2017 on work by Myles Allen and others demonstrated that methane’s GWP was more like seven times not 28 times that of CO₂. 

Despite the above, the discredited GWP figures are still locked into core New Zealand policy assumptions. They underpin or provide context for New Zealand’s greenhouse gas inventories, the Paris Agreement, and the Climate Change Commission’s work more generally.

Effort needs to continue with methane since our dairy and sheep industries mean New Zealand is a high emitter on a per capita basis.  This is visible to other countries that may seek to hold us to account, perhaps to advantage their own agricultural industries.  However, scientists have not yet developed credible solutions to methane emissions. We should not “risk the family farm” through punitive action on agricultural gases since under any scenario our emissions and their global impact will be vanishingly small. 

In a 2018 special report, the IPCC stated that to limit global warming to 1.5°C above prein­dus­trial levels we must also extract carbon from the atmosphere as well as reduce emissions.  That is, we need negative emissions technologies (NETs) as well as emissions abatement.

NETs in theory include conversion of pastoral grazing land into planted forest. However, this works only for the limited time that species such as radiata pine are growing and sequestering carbon.  It also conflicts with the Paris Agreement that addressing climate change “should not threaten food production.” 

“Carbon farming” through tree planting has seen pine monocultures take pastures out of food production and made land-use less flexible. Once the trees are planted little maintenance work is needed.  As farming jobs disappear rural communities are vulnerable to decline as small businesses close and public services are “rationalized.” 

IPCC experts have judged that direct air carbon capture and storage is too energy-intensive, and therefore too expensive. The venture capital firm DCVC concurred with the IPCC in a 2023 analysis and found that all such approaches it evaluated faced “multiple feasibility constraints.”

Peat soils, salt marshes and other wetlands usually have high carbon storage, as organic matter accumulates in wet conditions. Unlike pine forests, wetlands are not fire hazards, they protect biodiversity, however there are limits to how much more carbon they can sequester.

Many initiatives are underway to use tree biomass as long-term carbon stores.  Some of these proposals are to harvest wood and bury it, perhaps with some chemical treatment to slow its decay.  Astoundingly, these initiatives are often launched by “high tech” start-ups with backing from luminaires such as Bill Gates.  Those involved seem unaware that indigenous people in Amazonia and West Africa for thousands of years were turning biomass into charcoal and using this biochar to lift soil productivity. 

In the Amazonia there are large areas of dark, high fertility soils amidst the region’s weathered, thin and acidic soils. These “terra preta” (dark soils) were likely developed by indigenous people who dumped food scraps, manure waste, ashes and charcoal into then thin and infertile soils in their settlements.  Over decades these dumps became carbon-rich swathes of high productivity soil sitting within otherwise infertile soil deserts.

Terra preta soils date back over two thousand years. They can be two metres deep. Terra preta soil seems to regenerate itself at a rate of around one centimetre per year through processes that are not fully understood. Glomalin may play a role. It is also possible that small amounts of char continually migrate down providing habitat for microbes as they process surface-cover biomass. The microbes and fungi live and die inside the porous media increasing its carbon (biochar) content.

Biochar is not soil or fertilizer. It is carbon with high porosity and Cation Exchange Capacity (CEC). Biochar’s porosity and CEC helps water and nutrient retention and recycling and are associated with enhanced microbial activity and with healthier and more diverse soil microbiome. 

The international evidence is that biochar improves crop yields, especially on low fertility, low carbon and acidic soils, and in drought-prone environments.

Biochar can remove pollutants and yet recycle nutrients and retain water.  It can be used to purify wastewater.  It can remediate contaminated soils.  It can be used for activated carbon, in paints, construction, packaging materials and medicines. Above all, biochar can sequester carbon over intergenerational time frames.

Given the opportunities biochar creates, it is puzzling why it has not been more widely adopted.  Why for example is forest slash not pyrolyzed?  Managing forestry slash could see mobile pyrolizers turn waste wood into biochar on site, with the biochar spread back into the soil. This would help restore soil nutrient levels, reduce soil acidity, help retain water in drought-prone soils, and permanently lift soil carbon stocks.

In the modern world there can be a lack of respect for indigenous knowledge in such distant places as the Amazonia and West Africa. 

Biochar is an inherently diffuse rather than concentrated resource and this means the industry is made up of smaller businesses, with a lack of big companies with a strong lobbying voice.  Decentralization in industry organization does not sit well with some politicians and officials whose focus is reporting to overseas bureaucracies rather than solving problems down on the farm.  Soil carbon is difficult to measure to earn carbon credits and to report on New Zealand’s compliance with international agreements. However, biochar lends itself to Māori businesses operating on inalienable Māori land and taking a long term, intergenerational view of their investments.                                                                                 

For any pyrolysis biochar project, the end outcome for the biochar itself must be decided. So must be the value-adding cascade that occurs from the pyrolysis stage through to the final use made of the biochar.  This will determine what biomass will be turned into biochar, the pyrolysis process settings such as temperature and duration, any co-produced products such as bioenergy, the key use for the biochar batch (such as reducing nitrous oxide emissions or nitrate pollution of water) and the final use for the biochar as a permanent carbon store.

Several actions are required for biochar to take off on a large scale in New Zealand.  There needs to be formal government recognition of biochar’s value as a safe, long-term carbon store.  Ongoing research is needed to refine the biochar lifecycle process from pyrolysis through cascading value-add applications to final soil sequestration. Arguments that biochar’s longevity in soil has not been proven are erroneous and amount to willful blindness.  Biochar has been reported to provide a minimum 1,000-year biochar life. Charcoal from Māori cooking fires has been dated at 700 years old.

There needs to be a visible and well-functioning marketplace for biochar carbon credits. Progress is being made. Digital platform toucan.earth is building the infrastructure to make it easier for carbon credits to be bought, sold and retired.  BeZero, a credit rating platform, awarded an A rating to biochar as an engineered carbon removal project. This rating was awarded after assessment against risk factors, such as additionality, over-crediting, leakage, and non-permanence.

In 2023 toucan.earth established a seamless connection with the Finnish Puro.earth registry, facilitating credit transfers between their platforms. The digital platform has introduced an additional criteria-based screening process for Puro.earth projects.  Businesses with the heft of Microsoft and Shopify are now buying biochar CO₂ removal certificates from Puro.earth. 

The Singapore Government, the World Bank and the International Emissions Trading Association in late 2022 created the Climate Action Data Trust. This aimed to improve the credibility of the carbon credit trade. It has since grown to cover 85% of all credits issued to date and is set to expand coverage even more in 2024.

There seems to be no logical reason for further delay in making biochar a key part of New Zealand’s climate change action plan.

So, what are we waiting for?