Sustainable postharvest processing of maize residues (Zea mays L.) into biochar for agricultural and environmental applications

This study was carried out to explore the potential of processing maize residues into biochar via self-purging pyrolysis. The ultimate goal was to identify the potential and challenges of processing maize residues into biochar using a self-purging pyrolysis reactor for agricultural and environmental applications. This dissertation starts with the development and assessment of a self-purging pyrolysis reactor, characterisation of the biochar and evaluation of the phytotoxicity of maize cob biochar. In the first chapter, a prototype self-purging pyrolysis reactor was constructed and tested for the conversion of maize biomass fractions (cobs, husks, leaves) into biochar. In the second chapter, the cob, husk, leaf and stalk biochars derived from the self-purging pyrolysis were characterised, and the influence of pyrolysis conditions on the biochar properties was investigated. In the third chapter, the phytotoxic effects of maize cob biochar treatments and application rates on the germination and seedling growth of cress (Lepidium sativum) were evaluated.

It was found that the production of biochar from maize residues via self-purging pyrolysis is a promising approach to utilize biomass waste and create value-added products for agricultural and environmental applications. The self-purging pyrolysis reactor should be further tested to produce biochar from other crop residues. Furthermore, other products (i.e. bio-oil and pyrolysis gas) from the self-purging pyrolysis should be collected and evaluated in future work. In order to increase food security by combating land degradation based on the use of maize residues in the pyrolysis process, the application of biochar as a soil amendment should be promoted and sustainable biochar production systems must be established.