EtaMax

The EtaMax project's objective was to obtain maximum energy generation by completely converting easily digestable, low-lignocellulosic wet biomass into biogas using an adapted high-load digestion process and closing all material cycles at the same time.

In order to reduce dependence on dwindling oil resources and increasing carbon dioxide emissions at the same time, the use of renewable energies represents a sustainable alternative. Here, the use of plant biomass for the production of bioenergy – electricity, heat or fuel – plays a crucial role. Nevertheless, to date the potential of waste biomass to produce biogas as well as its use as fuel has been underexploited so far.

The EtaMax project consortium has thus set itself the objective to obtain maximum energy generation by completely converting easily digestable, low-lignocellulosic wet biomass – in particular cost-effective biowaste and algal biomass into biogas – using an adapted high-load digestion process and closing all material cycles at the same time. For the first time, digestion of fruit and vegetable waste in changing composition could be carried out in a long-term operation under continuous conditions with a retention time of 17 days and in a stable manner with high degradation level and high biogas yield.

The material cycles were closed by utilization of the biogas (as a fuel) and utilization of the digestate (for cultivation of algae). Purified biomethane was used as a fuel to power CNG (Compressed Natural Gas) vehicles. Liquid, nutrient-rich digestates accruing during digestion were used to cultivate microalgae, since the residues contain a sufficient quantity of inorganic nutrients required for the growth of algae.

The project "EtaMax" was funded by the German Federal Ministry of Education and Research (BMBF).