Systematic Quantification of Biogas Potential in Urban Organic Waste

Currently, there is growing interest in introducing the separate collection of biowaste from households, restaurants and commercial and industrial sources for biological treatment and the recovery of energy and nutrients. Upcoming policies and legislations promote and incentivise the production of biogas from organic waste rather than incineration and landfilling.

The production of biogas from urban organic waste is expected to contribute to reaching the EU target of 20% of overall energy production and 10% of vehicle fuel derived from renewable sources by 2020. The Danish energy strategy is for Demark to become a 100% fossil fuel-free nation by 2050. However, existing technical challenges and barriers must be overcome to make the production of biogas more attractive.

In this respect, a systematic quantification of the biogas production potential of various urban organic waste sources is necessary, in order to analyse and improve processes for biogas production. Conventionally, the potential biogas production of organic waste sources is quantified through biochemical methane potential (BMP) analysis and anaerobic digestion in biogas reactors.

However, the determination of BMP in batch incubation tests, and monitoring of production in laboratory reactors, for example, is considerably time-consuming and lasts from 30 up to 90 days, or sometimes even longer. Analytical and modelling methods were combined to develop a rapid, reliable and robust method for the BMP prediction of urban organic waste sources.

In total, the methane potentials of 87 urban organic waste samples were determined. In addition, 88 plant biomass samples were included in the dataset used for building a combined methane prediction model based on near-infrared reflectance spectroscopy (NIRS). The model was moderately successful in predicting the BMP of urban organic waste sources and could potentially replace traditional techniques currently employed for BMP measurement.

The model provides firsthand estimations of BMP and biochemical transformation in fewer than 72 hours, and it could provide support to biogas plant operators seeking to characterise substrate quickly, thereby enabling rapid decisions to improve methane production, optimise feedstock management and help identify slowly degradable feedstock before making a decision on which materials to utilize in the digesters.