Year: 2016
Type: dissertation
Abstract: Pyrolized carbon, also known as biochar, is a widely used soil conditioner recognized for its adsorption, C sequestration and agricultural qualities.This led to the investigation into the possible use thereof by small-scale sustainable farmers as a filter for agricultural olive or wine effluent, where after the spent biochar can be incorporated into composts to sterilize it from toxins and pathogens before being used as soil amendment.However, before these used biochar filters can be applied to compost, research is required to assess the affect that biochar could have on the composting process.This research project was therefore initiated to investigate the feasibility of adding biochar to composts, specifically focusing on the effect of type and amount of biochar on the composting process and mineralisation of the composts in soils.The final aim was to construct a method for quantifying biochar content in compost and soil that can be used to assess the stability of biochar in soils.Furthermore, none of this research has previously been done in South Africa or on two locally produced biochars.The first experiment was constructed to evaluate the effect of two contrasting commercial biochars on composting; a relatively low-cost, crude, pine wood biochar produced using a lowtech slow pyrolysis technique at 450°C, and a significantly more expensive, refined eucalyptus biochar produced using a high-tech slow pyrolysis technique at 900°C.The biochars were applied at two application rates (10% and 20% dry weight) to a mixture of green and animal waste.The effect was measured through composting indices such as temperature, C/N ratio, pH and EC, and microbial activity.Results showed that the robust, low temperature pine biochar applied at 10% (d/w) is the most suitable for composting due to higher composting temperatures measured, lower C/N ratios in the final product and higher cumulative microbial activity relative to the other biochar treatments.However, all biochar and control composts were all classified as successfully matured and stabilized according to the indices used, indicating that both types of biochar and application rates can be used to produce compost.The second experiment was aimed at comparing the carbon (C), nitrogen (N) and phosphorus (P) mineralisation of the composted biochar in relation to compost with biochar and biochar only under ideal laboratory conditions.The incorporation of these treatments into the soil showed that the composting process increased the composted biochars degradability with 7.6 -11.7% more carbon dioxide (CO2) being respired than compost with biochar of the same quantity.Biochar type and quantity influenced the mineralisation as eucalyptus char in general, and all treatments containing 20% biochar proved to be least degradable by microbes.Nitrogen mineralisation
Author: Ockert Guillaume Botha
Language: English
Subfield: Soil Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2602600846