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Abstract
Large areas of agricultural land are being degraded due to the rapid growth in population and poor land management strategies. Biochar has the potential to serve as a soil amendment. Biochar, which includes organic and inorganic components, is obtained from pyrolysis of feedstocks at low temperatures under a limited supply of oxygen. Biochar properties are influenced by feedstock composition and pyrolysis conditions.
To produce a value-added biochar and reduce production costs, this project investigates two innovative strategies: 1) production of mixed-feedstock-biochars rather than single-feedstock-biochar since they can provide almost all plant nutrient requirements 2) Converting nutrient-rich-biowaste into an engineered biochar through a controlled pyrolysis conditions. However, the agronomic benefits of biochar are dependent on its structural characteristics, which will, in turn, affect soil properties once it is applied. In particular, characterization of the organic component of biochar is essential since organic compounds influence soil organic matter and nutrient availability.
The objective of this project is to characterise, using a range of advanced analytical techniques, the properties of the organic components in: 1) mixed-feedstock-biochars, produced from a mixture of wheat straw and chicken litter, and a combination of wheat straw and basalt, 2) biochars produced from municipal solid waste at three temperatures (ranging from 450-650 °C). The positive effects of these available feedstocks on soils have been individually documented.
High temperature biochars had a high C and ash contents, but low O and H contents. Increases in pyrolysis temperature led to aromatic C structures and developed pores. Thus, the biochars surfaces were thermally activated to absorb nutrient elements that can further affect plant growth. Conversely, to preserve the N content, biochars should be produced at lower temperatures (<550 °C), since nitrogen was removed as a volatile matter during heat treatment. A significant decrease was observed in the concentration of dissolved organic carbon during pyrolysis, with an associated decomposition of hydrophilic fractions into low molecular weight acids (about 50%).
Overall, it is possible to match biochar with specific soil to address different soil requirements. The novelty of this project is to develop engineered biochars and manage waste, with economic and environmental benefits.