- Anthropogenic warming results from fossil fuel use, deforestation and soil carbon loss disrupting carbon cycles and elevating atmospheric CO2 Internationally, the top climate change priorities are reducing fossil fuel emissions, and stopping carbon losses from deforestation and from wetlands and peat soils. We must also reduce nitrous oxide (N2O) and methane (CH4) emissions. We must do so while supporting food security at a time of growing world population, and while transitioning away from many unsustainable industrial, energy and natural resource use practices.
- There is more carbon in soils than in plants and the atmosphere combined. However, since agriculture emerged around 12,000 years ago about 133 billion tonnes of carbon has been lost from soil (Sanderman et al., 2017). We must stop mining soil carbon.
- Under the Paris Agreement, 195 nations have committed to holding the increase in average global temperature to well below 2 °C above pre-industrial levels, and to strive to limit the increase to no more than 1.5 °C above. This requires “a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of the century”.
- The IPCC notes that even massive reductions in carbon emissions will be inadequate to achieve carbon neutrality by 2050, and that large-scale atmospheric CO2 removal is needed to prevent overshooting the 1.5°C temperature threshold.
- The IPCC has designated pyrolysis biochar as a credible negative emissions technology (NET) capable of contributing to large-scale removal of CO2 from the atmosphere, and this is triggering increased research and other investment in it.
What is biochar?
- Biochar is charcoal made from biomass and added to soil as a long-term carbon store, to lift productivity, and to protect the environment. Most soil carbon is labile, that is it decomposes and re-emits CO2 back into the atmosphere (as part of the fast carbon cycle). In contrast, pyrolysis transforms biomass into biochar – carbon that can be stored in the soil long-term. That is, pyrolysis biochar converts fast cycle to slow cycle carbon.
- Biochar is not soil or fertiliser. It is carbon with high porosity 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 can have positive benefits in animal and plant health and in bioremediation. It also reduces soil acidity.
- Between its pyrolysis production and its end storage in soil biochar delivers “cascading benefits” such as productivity gains, and wider bioremediation and environmental benefits. These benefits include reduced N2O and CH4 emissions, and reduced nitrate loss into water. The pyrolysis process also delivers valuable energy by-products.
- Conserving and recycling nutrients is essential for long-term sustainability. Modern farming systems are often energy-intensive and depend on synthetic nitrogen fertiliser made with non-renewable natural gas. High quality (low contaminant) phosphate is a scarce and increasingly politically locked-up resource. Biochar in soil can reduce nutrient leaching and improve nutrient recycling and its bioavailability for plants (Major et al, 2009). Biochar can form part of slow release and “enhanced efficiency” fertilisers.
How does biochar compare with other negative emission technologies (NETs)?
- Fuss et al (2018) include biochar in a list of NETs that have multi-gigatonne sequestration potential by 2050. Table 1 in Appendix 1 attached compares the benefits, costs, acceptability, and likely impacts of different NET options.
- The most important comparison is between biochar and Direct Air Capture of CO2 (DAC). DAC machines suck CO out of the atmosphere and it is stored, for example underground. DAC can involve use of hydroxide solution, or of amine adsorbents in modular reactors.
- DAC is capital and energy-intensive. It offers no clear productivity or wider environmental benefits. DAC raises questions about how CO could be stored in a geologically secure environment for centuries, given for example earthquake risks. Injection of DAC CO2. underground may impact on aquafers, with effects similar to fracking.
- Unlike other NETs, biochar produces a valuable product with multiple economic and environmental applications. Schmidt et al (2018) conclude that pyrolytic carbon capture and storage (PyCCS) can aspire to carbon sequestration efficiencies of >70%. They note that PyCCS does not create environmental hazards and that global scale-up is feasible within 10-30 years.
- Smith (2016) concluded that soil carbon sequestration and biochar addition to land had lower negative impacts and fewer disadvantages than other NETs. Biochar could be implemented in combination with bioenergy with carbon capture and storage.
- Hepburn et al (2019) reviewed 11,000 papers in assessing ten pathways for CO2 utilisation and removal, including biochar. Biochar is competitive with other pathways, depending on a range of productivity impact, carbon pricing and other assumptions. Pratt & Moran (2019) compare marginal cost curves of different abatement options. They conclude that even the most expensive biochar projects rival the cost effectiveness of alternative NETs.
- Gaunt & Lehmann (2008) found that biochar and bioenergy production combined with applying the biochar to agricultural land avoided between two and five times the emissions compared to when biomass was used solely for fossil fuel energy offsets. They also concluded that revenues from carbon emissions trading alone could justify maximising a pyrolysis plant for biochar production. Therefore, combining pyrolysis for bioenergy production with biochar carbon sequestration is more effective than producing solely bioenergy.
- Biochar lends itself to diffuse, small scale applications. However, large numbers of pyrolysis plants and biochar applications can aggregate into high carbon storage at the nation state and global levels.
- Overall, an increase of terrestrial and marine biomass production including long-term carbon sequestration via pyrolysis is considered the NET strategy that may be implemented the most rapidly, and with the lowest risk for other geological and ecological processes.
Political economy and technological system challenges for biochar
- Biochar faces political economy and technological system challenges.
Biochar is an inherently diffuse technology
- A barrier to widespread biochar adoption is the lack of concentrated business interests who can advocate for its adoption. This can be countered by a change in economic strategy, and a supporting “spirit for our times” zeitgeist that diffuses power and opportunity.
- Pyrolysis can be undertaken in large-scale continuous production industrial plants right through to small-scale batches in a backyard. Larger-scale plants can deliver co-products such as heat, power or chemicals. At the smallest scale biochar can be produced in a home log fire, while at a farm scale biomass can be pyrolyzed in a pit to produce biochar with minimal capital cost.
- Overall, biochar is a diffuse resource. As Roberts et al (2010) noted, transportation costs are a hurdle to the economic profitability of some pyrolysis biochar systems. As at 2010 they contended that biochar may only deliver climate change mitigation benefits and be financially viable as a distributed system using waste biomass. Mobile pyrolysis kilns can be moved to where the biomass is to support a distributed system that depends on seasonal or other “lumpy” biomass production flows, for example forestry harvesting skid sites.
- Like biochar, renewable energy sources such as wind and solar tend to be dispersed resources, and they can contribute to sustainable rural communities. A system that facilitates decentralised biochar production on thousands of small-scale sites helps normalise the diffusion of economic power. Such a distributed system complements a more decentralised energy system as farmers, small businesses and householders integrate solar panels, heat pumps, wind turbines and micro-hydro into their businesses and their lives. These distributed systems also enhance rural community resilience.
- Distributed generation can strand capital assets and depreciate their value. However, there is potential to repurpose stranded assets. For example, the gas and coal-fired Huntly power station could be converted into a biochar production plant.
Biochar as a NET is at an early developmental stage
- Biochar is a very old technology for agricultural applications, however it is at an early development stage when used as a NET. Much climate change mitigation R&D aims at centralised, high technology and geoengineering solutions. The policy advisory community can struggle with such concepts as repurposing indigenous technologies to deal with modern world challenges.
- However, pyrolysis biochar is becoming mainstream within the research and applied technology community. It is supported by world class basic science and applied research. With the rapid scientific and technological progress being made, biochar will become more cost effective and more precisely customised for specific applications.
- As biochar moves from a developmental to an operational stage, demand for biochar production will trigger a supply response and scale economies will emerge. Biochar demand will create opportunities for New Zealand manufacturing businesses to make kilns, pyrolysis plants, energy co-product systems and other equipment. As biochar is widely adopted a contracting industry will emerge, including with mobile pyrolysis plants configured around seasonal use. Many other uses for biochar beyond agriculture will be exploited.
Biochar is a multi-purpose product
- Pyrolysis biochar is a multi-purpose technology that produces different products and services that have different “price” structures (and sometimes no price at all). For example, pyrolysis bioenergy may be valuable if produced close to an industrial heat user, but not valuable elsewhere. Biochar may deliver “bankable” cascading services such as crop yield increases, but the biochar’s end use in carbon storage may not be valued. The economics change dramatically if carbon credits are awarded for biochar placed in soil.
- Roberts et al (2010) noted that the economic viability of the pyrolysis biochar systems they compared is largely dependent on the costs of feedstock production, the pyrolysis process, and the value of carbon offsets. These costs and values can change enormously, and with this the economic assumptions change.
- We need to assess and put value on the wider benefits biochar can deliver. For example, Biederman et al (2013) in a meta-analysis drawing on 317 independent studies looked at a range of economic and ecological benefits. They concluded that, despite variability due to soil and climate, biochar addition to soil resulted on average in increased crop yield, enhanced soil microbial biomass and higher soil carbon levels compared with control conditions. They noted that “the central tendencies suggest that biochar holds promise in being a win-win-win solution to energy, carbon storage, and ecosystem function”.
Biochar appears to improve its functionality with time, rather than depreciate in time
- Biochar is an unusual economic good because of its enduring presence in soil, and because over time its functionality can improve. Biochar may be costly to apply initially, however once in the soil it enhances productivity over the long-term. Based on analysis of terra preta soils in Amazonia, it is also plausible that biochar functionality improves over the very long-term.
Specific opportunities for biochar in New Zealand’s food and fibre (primary) industries
- Specific opportunities for biochar include:
Cattle and dairy farming
- ANZBI (2019) records financially profitable weight gains from feeding biochar to cattle in Australia, with the biochar ending up in the soil as a carbon store. Cattle farming productivity was increased with as little as a 1% biochar addition to stock feed.
- At the 2019 ANZBI conference results from biochar use in recent Australian dairy farm trials were reported. These trials indicated that biochar lifted dairy farm productivity and net profit substantially, as well as delivering soil carbon store benefits. However, it is unclear whether such results could be mainstreamed to all Australian dairy farms, let alone to New Zealand dairy farming systems. The Australian results were for intensive feeding of cattle rather than extensive pastoral grazing.
- Profitability is heavily influenced by biochar costs. The ANZBI-reported trials used biochar priced between A$100 to A$6,750 tonne – a huge variance that makes a big difference to the economics. The lowest price was for an industrial waste product. The economics greatly improve when biochar is a by-product of other processes such as bioenergy production, or when the biochar is made from waste that would otherwise be costly to dispose of.
- Farmers and orchardists can make their own small biochar batches cheaply and use them on their farms or orchards. Such production might have minimal capital costs, though it could be labour intensive.
- N2O emissions and nitrate loss that harms water quality are big challenges in dairy farming. Many studies are relevant to addressing such issues (see Clough et al, 2013; Steiner et al, 2010; Huang et al, 2014). Hestrin et al (2019) provide insight into the chemical bonding mechanisms through which biochar enhances nitrogen management while minimising air and water pollution.
- Biochar could capture nitrogen and other nutrients from dairy farm drainage and slurry pond Nutrient-laden biochar could then be added to soils to lift productivity and become a permanent carbon sink. There is also a lot of research underway internationally on using biochar to lower CH4 emissions from soil.
- Activated charcoal (including biochar) has long been used in veterinary medicine for animal health. This could have particular significance in the dairy industry, however the benefits are much wider. Schmidt et al (2016) and Toth & Dou (2016) report that biochar may boost feed conversion rates and improve stock health for poultry, pig and fish farming as well as cattle industries. Biochar may reduce antibiotic use in intensive animal industries.
- Biochar has shown promise as a feed additive to inhibit methanogenesis in ruminants. It is in use in the EU for this, and is also employed in bedding for wintering barns and poultry operations where its denitrification attributes can improve stock health and reduce farm costs.
Integrated dairy composting barn system incorporating biochar
- Composting barn systems can be used to improve cow welfare and reduce negative environmental impacts. They are being trialled in New Zealand. The barn system needs dry biomass such as miscanthus or sawdust for the cows to lie on. Cow wastes can be absorbed, and composted together with biochar, and incorporated back into the soil as an enriched amendment and a carbon store.
Sheep and beef farming
- Sheep and beef farming involves extensive grazing undertaken on many different soil types and topographies. Biochar making would need to draw on different biomass sources and the biochar tailored to different conditions. Biochar could reduce liming needs on acidic soils. In sufficient quantities it could improve water retention on drought-prone soils.
- Tree, berry, vine crop regimes and greenhouse horticulture produce pruning and other biomass waste from which biochar can be made. This can be used to improve microbial activity, nutrient recycling and bioavailability, reduce fertiliser input costs and improve water retention.
- In Australia trials with mixing biochar into topsoil around avocado trees have lifted productivity and been profitable. Biochar has also had plant health and crop quality benefits in macadamia trials. When biochar prices are high it is often only economic in targeted applications for high value crops, for example when added to tree or vine root zones. Banded application of biochar is more effective than uniform mixing in the soil.
- Biochar can enhance plant health – see for example Elad et al. (2010). Wood vinegar is a liquid by-product from the volatile pyrolysis gases. It has fungicidal and other properties. In the right quantities it can improve seed germination and enhance plant health.
Arable (including cereal) and vegetable growing
- In arable crop and vegetable growing biochar could be used to improve nutrient cycling. This could reduce fertiliser input costs and lift productivity. Biochar can improve soil structure, foster microbial life, and enhance water storage. It can have plant health benefits, including lifting crop seed germination rates.
- There is strong international evidence of biochar delivering large yield increases in tropical soils – see: http://www.pronatura.org/?page_id=521&lang=en . However, the evidence suggests that fresh biochar is unlikely to have significant, positive productivity effects on fertile temperate soils in the short-term. This is because it can reduce plant nutrient availability by binding and immobilizing nutrients. It may also feed a bloom of microbes that use up nitrogen in the soil, depriving plants.
- However, these problems can be corrected by adding a small amount of fertilizer to the biochar or soaking it in liquid nutrient before biochar is added to soils. For example, biochar used for dairy effluent filtration would capture nutrients, and the nutrient-rich biochar could then be added to soil.
- Ye et al (2019) did a meta-analysis of one year field trials on crop yields, using different biochars with a range of management practices in different soils and climates worldwide. These trials involved biochar, inorganic fertilizers (IF) and organic amendments (OA). Key findings were that, compared with a non-fertilized control, a 26% yield increase was observed with the use of IF only. When biochar was added (at 10t ha or less) with the IF a 48% increase occurred. When the control was IF, the addition of biochar added 15% to 19% to crop yield.
- Crop yields did not increase if more than 10t ha of biochar were added. Use of biochar alone did not increase crop yield. Evidence suggests that the beneficial biochar impacts were more through CEC than through liming effects.
- A meta-analysis by Jeffery et al (2011) found that crop productivity increased by 10% on average following biochar soil amendment. However, yield effects ranged between positive and negative with different soil types, environmental, and management conditions.
- Further effects of biochar amendments include lower emissions of N2O, with lower CH4 emissions measured especially on flooded soils (Kammann et al, 2017). Biochar can also have a positive effect on a soil’s water balance. On temperate soils, a 16% reduction in water losses was measured, which at the same time reduced the negative effects of soil dryness on microbial abundances by up to 80%.
- Dokoohaki et al (2019) noted that there was huge variance in biochar’s impacts on crop yields, depending on soil type and other factors. A consistent finding was biochar had low or negative impacts on yields from soils with high soil organic matter (SOM), high CEC and high pH soils, and high yield impacts on soils with low SOM, low CEC and low pH.
- They noted that lowering soil acidity likely results in increased microbial activity that in turn enhances nutrient availability. They forecast that enriching soil with biochar could increase U.S. crop yields by between 4.7 and 6.4 percent, with improvement more marked when applied to less productive soils.
- Economically profitable yield increases from biochar applications in maize growing have been reported from China. The Chinese experience is that biochar-enhanced chemical fertilisers can be profitable. However, there is little evidence so far of economic returns from biochar applications in arable farming in developed, temperate countries, with the exception of some crops.
- Keske (2019) concludes that it is economic in Canada to use black spruce biochar to grow potato and beet crops. In Australia, biochar applied at around 145kg per ha has significantly improved potato production. However, biochar has not so far proved economic in Australian broadacre cropping on a large scale (ANZBI, 2019).
Municipal waste management
- Municipal biomass waste is costly to dispose of, and if deposited in landfills CH4 is often emitted. Pyrolysis can turn waste into value whilst reducing emissions. Biochar can also adsorb excess nitrate and phosphorus from effluent before it is discharged. Large-scale pyrolysis in municipal and other waste plants can produce energy for cogeneration or process heat as well as biochar. For example, in Sweden and Finland pyrolysis bioenergy is used for district residential heating and industrial process energy, as well as biochar production.
- Massey University researchers are researching the economics of producing biochar from municipal sludge. Avoidance of tipping fees can make biochar so economic that municipal authorities could afford to deliver this biochar to farmers for free. Such biochar would be especially valuable to farmers if the biomass source had high ash content and fertilizer value.
Home garden, urban trees, parks and amenities
- While biochar is perceived as a product for the agricultural industries, it has widespread urban applications. These include niche applications such as in potting mix (as a peat substitute) for home garden or landscaping use, and biochar to improve urban tree health. In Stockholm, urban trees often had plant health problems and high mortality rates. Over about a decade these problems have been solved through modifying soils around the trees with biochar. In some cases, six year old trees planted in biochar-modified soils are five times larger than 30 year old trees planted without it.
- Biochar can also be used for urban amenity turf applications. For example, ANZBI (2019) recorded high economic returns from biochar used to enhance water efficiency in an arid region Californian golf course.
- Radiata forestry can impinge on soil fertility and acidity. Forest debris left to itself decomposes and releases CO2. It can also create environmental risks through downstream damage from storm events, as we learnt in June 2018. Turning such debris into biochar on site through mobile pyrolysis plants and applying it to forest lands could remove downstream hazards as well as sequester carbon for the long-term.
- While biochar made from forestry residue has high carbon content it would not add much to soil nutrient levels. However, biochar alkalinity can reduce soil acidity and enhance replanting of seedlings for the next forestry rotation. Solla-Gullon et al (2008) report reduced radiata mortality and higher growth in biomass due to biochar application in control plots in Spain. Thomas & Gale (2015) in a meta-analysis report large tree growth responses from biochar applications.
- On amenity and conservation lands, wilding pines and other invasive plants can be converted to biochar, offsetting control costs.
Forest processing waste
- A big opportunity for the forestry sector may be making biochar from wood waste. This can range from slash left after forestry harvesting through to sawdust. A wood processor turning logs into sawn timber or more elaborately-engineered products could convert wood waste into biochar and use the pyrolysis heat to dry the high value processed wood products.
- It is noted that switching from coal to wood bioenergy in industrial applications will create more demand for wood waste, and so biochar will need to compete with this alternative use. However, biomass boilers can be designed to produce biochar as an output alongside process heat.
Miscanthus for bioenergy and biochar co-production
- Miscanthus can be used for bioenergy production such as renewable diesel fuel (RDF). This can reduce fossil fuel emissions, with biochar made as a by-product. Miscanthus can be integrated into intensive dairy farm production, into extensive sheep and beef farm regimes, or it could be grown as a dedicated crop. Similar opportunities may come from hemp, including where it is grown for seed and produces fibre suited to biochar.
Intensive animal industries
- Pig and poultry industries produce concentrated, high nutrient waste. Some of this can be made into biochar, however it seems likely that most would be best turned into compost with biochar added to it to enhance its quality.
- Adding biochar to feed may have also have animal health benefits, and may help with reducing antibiotic use in intensive animal industries. Biochar incorporated into bedding may, through denitrification, reduce ammonia gas levels in broiler barns.
- Compost by itself is quickly broken down in soil by microbial processes. Adding biochar to it makes a more humified, stable and biologically productive form of compost. Adding biochar even in small amounts (e.g. 2-10%) can have big positive impacts on compost quality, and also deliver wider environmental benefits.
- Following the addition of 2% biochar to compost, Jindo et al (2012) recorded a 10% increase in carbon captured by humic substance extraction and a 30% decrease of water-soluble, easily degradable carbon. They also found an increase of fungal species diversity in the mature biochar compost, as compared to the control. They inferred that these fungi were responsible for the increased humification. Co-composting of biochar with nitrogen-rich manures can reduce nitrogen losses due to ammonia volatilization by up to 50% (Steiner et al, 2010).
Short-rotation coppicing of poplar, willow or other species
- Short rotation coppice (SRC) plantings can use fast-growing species such as poplar or willow. These are easy to manage and to harvest mechanically, and can yield 10-20 tonne per ha per annum of dry matter within two to three years of planting. Each tonne of biomass could yield 300-500 kg of biochar under different process conditions.
- As an example, if a 300 ha dairy farm planted 5% percent of its area in SRC, using its least productive land or riparian margins from which cattle are excluded to protect water quality, it could be making biochar and storing around 80 to 100 tonnes of carbon annually. Scaling this approach across the dairy sector as a whole, this could total around 2MT pa of CO2 removed from the atmosphere, with only minor alterations to land use and farm practices. This takes no account of other wider productivity and environmental benefits.
- Sheep and beef farms typically have a higher percentage of less productive land than dairy farms. This means more opportunities for growing poplar, willow and other biomass for biochar production. However, topography would make mechanical harvesting more difficult on some sites.
- Honey is harvested from manuka growing wild, typically on low fertility soils. Manuka is a succession species – left to itself other species will grow through and suppress it. Efforts are underway to systematise plantation production to optimise honey output sustainably.
- One possible production regime would be continuous harvesting and replanting of manuka to maintain ongoing honey, oil and wood production, with wood turned into biochar, perhaps with pyrolysis by-products such as energy. Coppicing is another option to produce biomass for biochar, while sustaining honey and oil production.
Tagasaste (tree lucerne)
- Tagasaste is fast-growing, and fixes nitrogen and provides fodder year-round. It is winter flowering and valuable for bees. It produces protein-rich fodder, is suited to varying climates and soils, and is drought-tolerant. Its roots can access soil nutrients as deep as 10 metres down. Tagasaste can be grown for biochar production. It can also be coppiced to provide ongoing biomass for biochar making, while also delivering fodder and other multi-use benefits.
What interventions are needed to catalyse mass adoption of pyrolysis biochar?
- New Zealand currently lacks a high-volume biochar supplier, which constrains trials with it. Biochar has been slow to win acceptance in New Zealand, however the Biochar Network New Zealand has built awareness, and the sterling work of Massey and Lincoln academics and research students has contributed to rapid growth in the international scientific understanding of biochar and to recognition of the key role it will play in future. However, there is still low awareness in the agricultural industry of what biochar can deliver.
- Biochar offers industry a positive opportunity to lift productivity, while reducing GHG emissions. It is more attractive than other NETs that have environmental risks. It does not stop farmers from farming, nor does it require radical changes in proven farming practices.
- To develop biochar into an effective NET and a sustainability technology in New Zealand we need:
- formal government recognition of biochar’s value and the roles it can play
- the formation and oversight of market(s) for sequestration credits
- end-to-end quality control and certification
- strategic funding of pilot demonstration projects
- information and extension services that share results from pilot projects, and allow biochar production and application to be continuously refined
Recognition of biochar’s value in climate change policy and for sustainability
- The IPCC recognises biochar as a credible NET, and this must be reflected in our formal climate change policy settings. We need to also promote biochar’s contribution to sustainable productivity.
- Soil carbon falls outside the Paris Agreement’s carbon accounting boundary, however it falls inside the international voluntary carbon market. Biochar needs its own sequestration status as a stable carbon form to distinguish it from short-term labile soil carbon.
- For biochar to earn carbon credits there needs to be a valid carbon accounting methodology and verification system. Verified credits can be monetised in the voluntary offsets market if buyers are secured. Buyers can be businesses that are willing to buy soil carbon rather than forestry carbon (for example in recognition of the implications of forestry carbon farming on isolated rural communities).
- In New Zealand, a market for biochar to earn verified carbon credits would incentivise biochar pyrolysis and allow scale economies to emerge. This market could involve a public or private entity or be a public-private partnership agency.
- Some Finnish businesses led by Fortum in collaboration with a financial services company and the Swedish bank SEB have established Puro, a marketplace that aims to make carbon removal from the atmosphere verifiable and tradeable through an open, online platform.
- Puro establishes a parallel voluntary mechanism for CO2 removal methods currently excluded from existing carbon pricing schemes. It issues CO2 Removal Certificates (CORCs) that are technology-neutral. It currently supports three CO2 removal methods – biochar, carbonated building materials, and wooden building elements. Links are at:
https://puro.earth/about-us/ and https://www.energylivenews.com/2019/04/18/finnish-firms-launch-worlds-first-hub-for-co2-removal-certificates/
- Large-scale biochar production and sequestration can be monitored efficiently so carbon credits are valorised. However, this is difficult with small-scale production at the farm or household level. Rather than incentivise small-scale production at the micro-scale with carbon credits, it may be better to offer free on-line optimisation information (or extension services) that enables small-scale players to maximise biochar productivity in their chosen application without claiming carbon credits.
An end-to-end quality control and certification system
- Biomass sources, pyrolysis processes, cascading uses, and end sequestration must be fit for purpose. End-to-end quality control is needed.
- A certification-based or other such verification system would need to validate how a biochar product was produced, its carbon and nutrient content, and its performance in specific applications. Such a system would provide confidence in biochar cascading uses and final sequestration in soils rather than, for example, use as a charcoal fuel. An authentication mechanism could be built into a blockchain system.
- Quality biochar starts with quality biomass. Biomass contaminated with toxic chemicals or metals should not be used in agriculture or horticulture. Biomass source influences biochar properties – for example wood-derived biochar has higher carbon content whilst food waste and manure-derived biochar has higher nutrient content.
- Pyrolysis process settings must comply with rigorous stack emissions and air quality standards. This must minimise release of flue gases with products of incomplete combustion, particulates that can damage air quality, and release of embers that create fire risks. This is achievable with large production plants, however it may be more difficult to achieve with small-scale operations.
- Process settings must be calibrated to achieve the desired balance between biochar, biogas and biooil (“wood vinegar”). This balance will be determined by the intended cascading use and the end biochar sequestration, and by the value of by-products such as energy. For a typical biomass, slow pyrolysis produces around 35% biochar, 30% biooil, and 35% biogas by weight. Fast pyrolysis produces around 20% biochar and 60% biooil and 20% biogas by weight.
- Pyrolysis temperatures influence biochar properties and long-term stability in the soil. Different biomass sources and pyrolysis conditions can be used to make biochar optimised for specific applications such as animal feed additives, maximising stable carbon sequestration, nutrient sorption or phosphate recycling.
- The European Biochar Certificate (EBC) is the voluntary European industrial standard. It is designed to ensure sustainable biochar production and minimise hazards to agronomic systems. These standards guarantee ecologically sustainable procurement and production of biomass feedstock for biochar production, compliance with emission standards, and environmentally safe storage. Biochar quality is comprehensively monitored, documented and independently controlled and complies with all threshold standards related to the Ordinance on Soil Protection.
- The EBC pillars are independent on-site control (government accredited), accredited laboratories, and legal backup. The EBC certifies sustainable provision and production of biomass feedstock, energy efficient, low emission pyrolysis techniques, biochar quality (low contamination), low hazard biochar use and application.
- New Zealand can also draw on Australian work on biochar end-to-end quality control assurance, or it can develop its own system.
R&D-based pilot demonstration projects
- Enough is known about biochar to focus R&D on some applied demonstration projects in “real world” New Zealand agricultural and horticultural production systems. Results from these projects can be promoted through on-line tools, and can support fine-tuning of biochar technology and its mainstreaming. Higher levels of investment should be made in the Biochar Research Centre at Massey, and in biochar-related research at Lincoln and Waikato universities.
Continuous learning and fine-tuning
- As biochar use expands and is applied to different opportunities it will be important to continuously learn from its productivity and environmental performance in different agricultural and horticultural settings. This will allow ongoing finetuning and optimisation, with results disseminated to those engaged in biochar technology.
- New Zealand’s biochar research must be linked to and leverage off the international research effort. We should be fast in identifying, testing and leveraging possible “game-changing” results. For example, Masek et al (2019) find that a low concentration potassium addition to biochar can improve its soil carbon sequestration effect by up to 45%. Potassium doping also increases nutrient content of resulting biochar, making it better suited for agricultural applications.
- New Zealand needs to quickly adapt scientific advances in biochar research, both domestic and international, and apply them to our own opportunities. In doing so, biochar can be a key part of our climate change response, while also lifting our productivity and sustainability.
Appendix 1: Comparison of negative emissions technologies (NETs)
Table 1: NET Comparision
|Direct Air Capture (DAC) of CO2
||DAC machines suck CO2 out of the atmosphere and it is stored, for example underground. DAC can involve use of hydroxide solution, or of amine adsorbents in modular reactors.
|DAC is capital and energy-intensive, see:
DAC offers no clear productivity benefits, except possibly if the CO2 is used for such purposes as enhancing greenhouse horticultural output. However, this would still lead to CO2 release as biomass breaks down. CAC has no wider environmental and bioremediation benefits. DAC raises question about how CO2 could be stored in a geologically secure environment for centuries.
||This can involve pulverising olivine or other materials to increase their surface area and absorb more carbon. This carbon can then be stored in seawater or soils.
||This is very capital and energy-intensive. It also delivers no wider productivity or bioremediation benefits.
||Iron or nitrogen could be added to seawater to encourage algal blooms, thereby absorbing more CO2.
|Creates risks of low oxygen dead zones. Would face international as well as local opposition.
|Blue carbon habitat restoration
||Restoration of salt marshes, mangroves, tidal wetlands, seagrass beds to act as carbon sinks.
Protection and where possible enhancement of wetlands and peat soils.
|Good strategy to follow, with wider environmental including biodiversity benefits. It is however limited by geographic constraints.
||Planting trees to sequester carbon.
||Afforestation (and avoiding deforestation) have key roles to play. However, there are limits to available land, and risks of crowding out food production at a time of rapid population growth.
Woodfield (2019) raises concerns that incentives for forestry planting for carbon sequestration in NZ are too short-term, and may have unintended negative consequences. He contends there is no clear “what next” strategy after carbon credits are earned on the first rotation, noting that harvesting incurs liabilities unless the forest is then replanted.
However, it might be possible to sustainably manage some permanent forests for co-products such as honey, edible fungi or coppiced wood as well as using them as carbon sinks.
|Using wood and other biomaterials to replace GHG-intensive materials.
||Sustainably-produced timber and other biomass can replace GHG-intensive materials such as concrete, steel and plastics. Examples include engineered wood in multi-storey buildings. With policy change, it might be possible to offset forest harvesting liabilities through credits for carbon stored in long-life wood products.
||This is an effective strategy, enabled by advances in multi-story wood engineering technology. Each tonne of dry wood that displaces concrete-based materials avoids nearly four tonnes of CO2 emissions (Sathre & O’Connor, 2010). However, global impacts may be small due to the limited quantities of wood that can be used in building.
It is noted that biochar as well as wood can substitute for carbon emission-intensive construction, infrastructure and packaging materials.
|Bioenergy carbon capture and storage (BECCS).
||Burning biomass to produce energy for electricity generation or process heat, with CO2 capture and storage.
|This avoids some fossil fuel CO2 emissions. However, it raises issues about how CO2 that is captured can be stored. There is concern that BECCS may be harmful to ecosystem services and biosphere integrity if implemented at scale (Boysen et al., 2016b; Burns & Nicholson, 2017; Heck et al., 2018).
Note that replacing fossil fuel use with bioenergy can reduce emissions, however this is not a NET because CO2 is not removed from the atmosphere. When bioenergy that replaces fossil fuel use is combined with biochar production and sequestration it is a NET.
|Enhancement of labile soil carbon.
||The importance of soil carbon sequestration is widely recognised. In 2015 the French Government launched a call for a 0.4% increase in soil carbon annually. Using farming techniques to lift labile soil organic matter (SOM) can help support this.
||Gains can potentially be made in lifting SOM by changing farming techniques. However, labile carbon turns over rapidly, releasing CO2 back into the atmosphere rather than being a permanent carbon store.
||Turning biomass into charcoal and using this biochar for productivity and bioremediation purposes before storing it in soil as a long-term carbon store.
||Unlike other NETs, biochar produces a valuable product with multiple economic and environmental applications.
Schmidt et al (2018) conclude that pyrolytic carbon capture and storage (PyCCS) can aspire to carbon sequestration efficiencies of >70%. They note that PyCCS does not create environmental hazards and that global scale-up is feasible within 10-30 years.
Smith (2016) concluded that soil carbon sequestration and biochar addition to land had lower negative impacts and fewer disadvantages than other NETs. Biochar could be implemented in combination with bioenergy with carbon capture and storage.
Pratt & Moran (2019) compare marginal cost curves of different abatement options. They conclude that even the most expensive biochar projects rival the cost effectiveness of alternative NETs.
Biochar lends itself to diffuse, small scale applications. However, large numbers of pyrolysis plants and biochar applications can aggregate into high carbon storage at the nation state and global levels.
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 The slow carbon cycle forms coal and oil over millions of years. The fast carbon cycle sequesters carbon in vegetation and soil and then releases carbon back into the atmosphere over months or years.
 Kelpie Wilson’s superb outline of how biochar functions in soil is at: https://www.biochar-journal.org/en/ct/32-How-Biochar-Works-in-Soil
 Biochar can store carbon for hundreds of years or more. The longevity depends on factors such as the biomass used, the pyrolysis process applied and soil and climate conditions. For policy purposes we can regard biochar as a permanent carbon store over the timeframes needed to avoid catastrophic climate change.
 There are many wider biochar applications that are not discussed in this paper. See link to 55 uses for biochar at: https://www.biochar-journal.org/en/ct/2 updated at: https://soilcarbon.org.nz/the-biochar-displacement-strategy/ Biochar can play a key role in a circular economy. Answering the question ‘what unsustainable resource use can biochar displace?’ will generate biochar innovation in many different fields. Albert Bates and Kathleen Draper co-authored a recent book on non-agricultural uses of biochar: BURN: Using Fire to Cool the Earth.
 Excessive synthetic nitrogen fertiliser leads to air and water pollution and harms the soil microbiome. Chen et al (2018) explores ways of reducing the need for fossil fuel use to meet nitrogen needs.
 This fits well with current plans to phase out coal use at the Huntly plant. The Huntly plant is close to both biomass sources and to dairy and other agricultural users of biochar. It is also located in a community that needs jobs and new business development.
 Massey University researchers have estimated a biochar production cost of NZ$400 per tonne for the purposes of assessing economic opportunities in New Zealand.
 One approach might be to use a floating mat of biochar on a slurry pond surface to bind nitrogen.
 It is difficult to gauge biochar’s long-term effects, though it seems that biochar functionality improves over time. Kelpie Wilson likens terra preta soils to well-aged cheese. These soils have been dated back thousands of years. They seem to self-generate, in that when terra preta soils are “mined” as potting mix, leaf and other plant material that falls onto these soils is colonised by biochar microbiome, forming new and highly productive terra preta soils but without enhanced carbon content.
 Some research in Taranaki and Manawatu suggests that biochar made from willow can lift clover growth for reasons other than liming effects.
 This is based on one tonne of carbon equalling 3.67 tonnes of carbon dioxide emitted.
 Some sheep and beef farms have large and unproductive poplar trees that could be turned into biochar.
 Manuka oil extraction requires harvesting biomass and bringing it to an extraction facility which requires process heat. Residue from this could be turned into biochar using an integrated oil extraction and pyrolysis facility.
 These projects could be supported by adaptable multi-user facilities to produce biochar with different characteristics for diverse research and pilot demonstration projects.
 Australia has made progress with carbon farming initiatives, including methodologies governing measurement and verification.
 Other businesses involved include Tieto, Valio, St1, ÅF Pöyry, Compensate Foundation, Carbofex, Yara Suomi Oy, Lassila & Tikanoja, SOK, Orbix, Nordic Offset and Hedman Partners.
 An example is tantalised timber.
 Singh et al (2012) report that the mean residence time (MRT) of biochar in clayey soil ranges between 90 and 1,600 years, based on limited laboratory trials using a range of biomass sources. They considered that the MRT was likely to be longer in field conditions.