Biochar in soil: Carbon sequestration, Soil quality improvement and Contaminant remediation

Project progress FriPro 217918, Dec 2017 WP1: Biochar, soil acidity, nutrient availability and soil biology Completed. The most important results from the new Zambia field trials include; i) the first field evidence that biochar retains water in dry African soils, this providing climate change mitigation as well as adaptation under drier conditions; ii) biochar moderates soil temperatures, probably due to its porosity. Indonesia: the most important finding is that biochar can be very effective on acid soils but that its effectiveness disappears after 3-4 seasons, because of wash-out of the alkalinity. In the Nepal pot trial we found that both alleviation of water stress, acid stress and nutrient stress play a role, but that the most important effect is probably nutrient retention. We did as planned a similar test in Zambia and got conformed there that water stress alleviation is the most important mechanism of biochar effect in these soils. WP 2. Biochar and toxic gas emissions Completed, apart from the methane research, that was done, but did not lead to any useful data. We constructed the novel flame curtain kiln in Nepal and performed gas emission measurements, and confirmed for the first time that the flame curtain kiln is the cleanest and simplest technology for medium-scale biochar generation in tropical settings. This is no less than a breakthrough and this kiln has been implemented in 70 countries already. WP 3. Pollutant and pesticide sequestration by biochar Completed. In collaboration with RECETOX, a leading ecotoxicity research institute in Brno, Czech Replublic, we addressed the effect of biochar amendment to soil on pollutant sorption, bioavailability, bioaccessibility and ecotoxicity. Our setup with various biochar dosages as well as both noncontaminated and contaminated soils allowed, for the first time, for the distinction between positive amendment effects in the form of reduced toxicity through strong sorption, and negative secondary amendment effects due to deleterious effects of the biochar particles themselves. The project has also led to a spinoff project funded by recycling company Lindum A/S in Norway (400 kNOK per year; 2017-2019), where we build on the knowledge generated in this project on contaminant immobilization by biochar. The idea is to combine two waste streams into a resource: biochar will be made from waste timber, and mixed into contaminated soil, reducing its contamination risk and leading to beneficial climate effects in the form of carbon sequestration. Spinoff project As a spinoff of this project, we have now got a new project funded under Dept for International Development (DfID, UK) for 4 years of testing implementation of biochar-pigeon pea agroforestry in conservation farming in Zambia, with 93 farms. The present NFR project has allowed us to solve all research issues connected to biochar use in Zambia, and now we are allowed to implement the concept.

Biochar is the charcoal product obtained when biomass (preferably organic waste) is heated without access to oxygen (pyrolysis). In contrast to organic material, biochar is stable > 1000 years when mixed into soils, and thus represents carbon that is acti vely removed from the carbon cycle, which mitigates climate change. In addition, biochar reduces release of the strong greenhouse gases (GHG) methane and nitrous oxide, improves degraded soil quality, and sequesters pollutants. Thus, biochar could provide an important wedge against climate change, while using waste as a resource and improving the quality of degraded or polluted soils. Currently many of the underlying mechanisms are still unknown, and research has largely been phenomenological and monodisc iplinary. Elucidating the mechanisms behind biochar amendment to soil would yield ground-breaking research with an enormous potential impact, enhancing its effects as a carbon sink and soil improvement, as well as aiding in creating carbon credit economie s, developing carbon reduction strategies, and reclaiming degraded soil. The core aim of the proposed research is to elucidate the mechanisms of biochar?s potential to simultaneously sequester carbon, improve soil quality and chemically remediate polluted soils in diverse environments. Unconventional, multidisciplinary approaches are proposed to unravel the mechanisms of biochar effects on soil quality: systematic lab and field studies on soil acidity, nutrient availability, GHG emissions, (de)nitrificati on, microbial populations, plant growth, biodiversity and pollutant availability will be undertaken. Elements will include leaching tests, passive sampler sorption experiments, gas sorption experiments, molecular modelling and X-ray microscopy. Thus a tra ns-disciplinary combination of environmental, soil, biogeochemical and climate science is envisioned to yield innovative and society-relevant research.