Recycling and utilisation of faba bean harvesting and threshing waste for bioenergy

Abstract

This article analyses and evaluates the impact of the technology of soil processing on the biomass indicators of faba bean waste. Samples from five different primary tillage systems were taken and analysed. The raw material of faba bean waste was processed and pressed into cylindrical pellets. The results of the experimental research of the pellet properties revealed that the content of moisture of the pellets from faba bean waste changed from 8.2% (deep cultivation, 3-GP) to 10.8% (untreated soil, 5-ND). The highest density of faba bean waste pellets was obtained from the sample of conventional soil ploughing, (1-IA) (1311 kg m−3), while the lowest density was recorded under shallow ploughing (2-SA) – 1275 kg m−3. The lower calorific value of dry biofuel from faba bean waste pellets was similar in all the samples and ranged from 16.9 MJ kg−1 (5-ND) to 17.1 MJ kg−1 (2-SP). The calorific value of faba bean waste pellets was relatively high and was close to the calorific value of some types of wood waste. The following harmful gas emissions were analysed and evaluated: carbon monoxide CO, carbon dioxide CO2, unburned hydrocarbons CxHy, and nitrogen oxides NOx. The harmful gas environmental emissions detected while burning the pellets of faba bean waste have not exceeded the permissible limits. The best results of the pellet properties, the content of ash and the emissions were obtained under conventional ploughing (1-IA) and deep cultivation (3-GP). The research results suggest that faba bean waste could be used as granulated biofuel, since the main parameters of this legume waste correspond to the basic requirements of solid biofuel. It was determined that under untreated soil (5-ND) technology the CO2 emissions eqv. were twice lower than under conventional soil ploughing (1-IA). These results show that no-till technology is suitable for sustainable agricultural practise both for producing the faba bean grain and for processing the pellets from the waste.