Once produced, biochar is used as a material, in combination with other materials, to make a “biochar product”. In other words, biochar is an input to the lifecycle of a “biochar product”, which has its manufacturing, use and disposal phases.
Beyond direct application of biochar to soils, biochar can be involved in a variety of products, in multiple industries: animal feed or food additive, manure management or biowaste treatment additive, specialised fertilisers, soil blends, filters, construction materials, electronics…
Inclusion of biochar in products leads to change in the formulation of the products. From a systems analysis perpsective, this relative change may lead to substitition of materials and shifts of environmental impacts.
Beside direct application of biochar to soil, biochar can be returned to soil in various ways.
Biochar compound fertilisers: biochar can be combined with organic or mineral fertilisers to form engineered fertilisers, both solid or liquid.
Solid biochar-based fertilisers can be granules or pellets, which are applied to soil by spreading.
Liquid biochar-fertilisers involve adding powder biochar to a nutrient-rich liquid such as slurries. The liquid mixture is then spread on fields either via irrigation techniques or existing machinery for liquid fertiliser injection.
Animal feed: several companies have developped biochar animal feed (e.g. poultry, dairy, horse, but also cats and dogs).
Co-amendment: biochar can be combined with compost or animal manure, before applications.
In urban areas, biochar is being used as a component for landscaping applications.
Component in maccadam-soil blends: biochar, compost and maccadam blends provide an aerated tree planting substrate well-suited for paved areas because of its mechanical properties. It has been in use in Stockholm since the early 2010s.
Component in mineral soils for green roofs: biochar is also being used as a component in mineral soils (i.e. made of clay, lava stones, and similar mineral components), suited for extensive green roofs.
Component in mineral other landscaping soils: biochar is also blended with compost and other minerals to provide an alternative to peat-based landscaping soils.
Additive in cement, concrete, and asphalt: biochar with specific properties and particle size can be used as an additive in cement and concrete products, replacing other components, and sometimes leading to improved or similar mechanical properties. Biochar addition to asphalt has also been investigated.
Component of water filters: biochar from various types of wood can be used as a carrier for biofilm growth, used in water treatment, with equivalent or improved performance relative to sand filters or other biofilm carriers.
Additive in plastics: biochar powder has also been used as an additive in plastic manufacturing, leading e.g. to improved mechanical properties and the ability to cast thinner products, reducing the use of plastic per unit of product.
At the biochar product manufacturing stage, the life cycle considerations are:
Identify the functions of the biochar-product (e.g. 1 plastic pot of 50 cm3 for horticulture)
Identify alternative products delivering an equivalent function (e.g. conventional plastic pot, paper-based pot)
Note any quality differences in the functions delivered (e.g. biodegradability of pot, resistance to moisture during storage or use)
Quantify material use, energy use, tranpsortation, but also direct emissions during manufacturing, for the biochar-based product and its alternatives.
Such modelling was performed in our Uppsala case, describing various biochar-products used in urban areas in Sweden.
To explore the topic further, we recommend the following references:
Azzi, E. S., Karltun, E., & Sundberg, C. (2022). Life cycle assessment of urban uses of biochar and case study in Uppsala, Sweden. Biochar, 4 (1), 18. https://doi.org/10.1007/s42773-022-00144-3
Jayakumar, A., Wurzer, C., Soldatou, S., Edwards, C., Lawton, L. A., & Mašek, O. (2021). New directions and challenges in engineering biologically-enhanced biochar for biological water treatment. Science of The Total Environment, 796, 148977. https://doi.org/10.1016/j.scitotenv.2021.148977
Papageorgiou, A., Azzi, E. S., Enell, A., & Sundberg, C. (2021). Biochar produced from wood waste for soil remediation in Sweden: carbon sequestration and other environmental impacts. Science of The Total Environment, 145953. https://doi.org/10.1016/j.scitotenv.2021.145953
Gupta, S., Kua, H. W., & Low, C. Y. (2018). Use of biochar as carbon sequestering additive in cement mortar. Cement and Concrete Composites, 87, 110–129. https://doi.org/10.1016/j.cemconcomp.2017.12.009
Mumme, J., Srocke, F., Heeg, K., & Werner, M. (2014). Use of biochars in anaerobic digestion. Bioresource Technology, 164, 189–197. https://doi.org/https://doi.org/10.1016/j.biortech.2014.05.008
Schmidt, H. P., & Wilson, K. (2014). The 55 uses of biochar. The Biochar Journal. https://www.biochar-journal.org/en/ct/2