This study evaluates the environmental impact of replacing natural gas heating and peat use in the horticulture substrate market by means of biomass gasification towards co-production of syngas and biochar. The produced syngas can provide sustainable greenhouse heating; biochar is currently considered as a peat substitute while it offers carbon sequestration potential when disposed in the soil due to its higher carbon recalcitrance compared to peat. The carbon footprint of four feedstocks is followed, namely willow and pine from tree nurseries, grade A wood pellets produced from demolition wood and park residues. The CO2 emissions timing is taken into account (time delay between harvest, decay and growth rates of organic matter, peat and biochar). Emission calculations from indirect land use changes (iLUC) are included for the two wood feedstocks (willow and pine). The feedstock source and physical properties have a high share in the environmental impact of the bioenergy production (process heat) and biochar. Peat replacement by biochar reduces the current pressure on the environment caused by peat extraction and use. When biochar is stored permanently in the soil as a disposal option, the corresponding negative CO2 flux further reduces the total CO2 emissions acting as a carbon capture and storage mechanism.
The paper uses a consequential life cycle assessment to compare the Enerchar system with current greenhouse practices: natural-gas heat and peat-based growing media. Its functional unit is 1 MJ of heat delivered, with the co-produced biochar included in the system. The boundary covers feedstock collection and preparation, gasification, use of syngas for heat, replacement of peat by biochar, and the spent substrate’s end of life in soil. The study models four feedstocks: willow, pine, grade A pellets made from demolition wood, and residues from municipal parks. It uses lab-scale process data from the Energy Research Centre of the Netherlands (ECN, part of TNO), alongside background inventory data. The assessment accounts for the timing of carbon uptake and release as biomass grows and decays, and for the stability of carbon in peat and biochar.
The results vary substantially by feedstock. The paper reports that slow-growing pine can lead to net CO2 release over a 100-year period, while fast-growing willow can provide a more favourable carbon balance through carbon uptake during growth. Park residues also perform well in the model, although their seasonal and variable properties can make them less suitable for some conversion systems. For the willow-based Enerchar case, the study reports a net global-warming result of −0.0113 kg CO2-equivalent per MJ of heat when biochar use and storage are included. The result reflects several linked effects: syngas replacing fossil heat, biochar replacing peat, and stable biochar carbon remaining in soil after use.
These findings depend on the modeled Dutch greenhouse, the chosen feedstock supply chains and assumptions about biochar use. The model assumes equal crop yields and watering needs with peat and biochar, and does not include potential changes in fertiliser demand or soil emissions. The authors stress that feedstock origin, growth and decay rates, carbon stability and competing uses can change the outcome; each supply chain therefore needs case-specific assessment. They also note that common standards for measuring the long-term stability of biochar carbon are still needed.
