TIMBIO: The production of biochar from waste timber for the remediation of soil contamination

There exist large amounts of lightly contaminated organic wastes such as waste timber (shredded wood panels from demolition, furniture, spent pellets), garden/forestry waste, food waste and sewage sludge. Society needs sustainable treatment methods that optimize resource use and minimize amounts of toxic substances and microplastics in these wastes. Conversion of organic waste products to biochar through pyrolysis (combustion in the absence of oxygen) can be such a treatment method, as it immobilizes/destroys contaminants. In the feasibility study, biochar was identified to carry a significant value as strong binding agent (sorbent) for soil remediation and purification of air and water, reducing the leaching, emissions and risk of these contaminants to the environment. There is currently much focus on the fertilizer properties of biochar, but our feasibility study indicated that its value as a sorbent far exceeds that as a fertilizer addition, up to 10 000 NOK per tonne. As an important co-benefit, biochar helps to combat climate change; it contains a lot of carbon and is stable for thousands of years, and thus its carbon is stored. Engineered "designer" biochars with optimized properties have not yet been made from waste timber residues, sewage sludge, or biological waste, or applied to real-world contaminated sites. The main project will aim at creating sustainable products for soil, air and wastewater treatment from organic waste fractions. The feasibility study indicated that the generation of biochar sorbents from organic waste fractions should thus not be limited to waste timber. Making high-value sustainable sorbents is equally relevant for other organic waste fractions such as biological waste incl. food waste, sewage sludge, and reject from biogas installations. The BIA-X network meeting and feasibility study gave the opportunity to identify various new partners for the consortium for a main project: waste and sewage handling companies (Lindum, VEAS), a technology provider (Scanship) with a network of waste producers (the cruise industry), and end users in both soil treatment (Lindum), water treatment (Mivanor) and gass/odor treatment (Lindum/Clairs). Lindum is interested in valorizing waste timber, garden waste as well as digestate and reject from their biogas plant. VEAS wants to valorize polluted sewage sludge containing microplastics and persistent pollutants to clean and sustainable biochar sorbents. Mivanor aims at improving their innovative flocculation-based wastewater treatment technology, that currently has an effectiveness of 60-70% for organic pollutants and metals, with the realistic aim of improving it to 90-95% by the use of designer biochar. The title of the proposed main project has been changed to reflect this wider angle: VOW: Valorization of Organic Wastes into Sustainable Products for Clean-up of Contaminated Water, Soil, and Air.

The study indicated that high value products can be created through sustainable biochar sorbents while addressing these SDGs; - SDG6, Clean Water: Biochar sorbents can be used as an innovative solution for cleaning sewage water and landfill leachate. A new consortium partner, Mivanor, will optimize its flocculation-based waste water treatment process with biochar sorbents. - SDG7, Clean Energy: Syngases and the bio-oil formed during pyrolysis can be converted to methane to be sold as an energy carrier. - SDG12: Organic waste streams are recycled into a valuable resource, improving efficient management of natural resources. Pollutants and microplastics in biowaste will be destroyed by the pyrolysis process. - SDG13, Climate change: The carbon in biochar is stable for 1000s of years, making biochar a mitigation strategy. - SDG15, Terrestrial Ecosystems: Immobilizing pollutants in soil with sorbents will reduce ecosystem stress and loss of biodiversity.

Norway has thousands of contaminated soil sites and 3.7 mill ton y-1 forestry residues. Lindum AS receives 250 000 ton y-1 waste timber residues from house and building demolition. A recent discovery is that biochar from waste timber strongly binds soil contaminants, reducing pollutant leaching to groundwater and aquatic environments, and increasing the possibilities for reuse of the contaminated soil. As co-benefits, due to the high stability of biochar and its high carbon content, the carbon in the waste timber will be sequestered (mitigating climate change). The effect of biochar on pollutant risk will be investigated for both perfluorinated compounds, "PFAS", currently at the forefront of the environmental authorities' interest, and heavy metals in shooting range soils or mine tailings. The main technologies to be investigated for "designer" biochar include activation and iron/sulphur enrichment. Thus, the primary overall objective of the project is to turn a waste into a resource by creating engineered charcoal ("biochar") from waste timber with properties optimized to immobilize organic and inorganic pollutants in contaminated soils. A combination of scientific/economic assessment is envisioned for the feasibility study. NGI will coordinate and lead the overall work, and characterize the waste timber, the biochars, and evaluate the overall environmental sustainability of the technology. Literature searches will be done for optimal processes to prepare designer biochars. To provide input for the sustainability assessment, NGI will visit an industrial-scale pyrolysis unit in Switzerland, and evaluate emissions of smoke and toxic gases, as well as the composition of the resulting biochar. Economic evaluation of various types of pyrolysis units will be done. In a possible main project, the designer biochars will be produced at an industrial scale, and tested in the field, so that the novel technology is ready for implementation.