Author(s)

S. Oldenburg, L. Westphal & I. Körner

Abstract

Not only due to the actual climate change, but also in consideration of exhaustible resources, alternative energy supplies for the steadily growing energy demand need to be found. The main emphasis should be placed on the substitution of fossil fuels with agricultural by-products and other organic materials. The utilisation of fresh grass or grass silage of extensively cultivated farm land especially has great potential as an energy feedstock, as in agriculture this bio-resource is currently considered a waste material and is neither economically nor ecologically utilised in an efficient way. Additionally, the lawn-clippings, which are accumulating as communal and private waste could be used for energy production since many local authorities have problems with utilising this gramineous waste. Thus, for anaerobic digestion big amounts of grass biomass and lawn substrates are available from farmers and landscape conservation. In order to evaluate the suitability of this material for biogas plants in the first place a detailed inventory needs to be conducted. This was exemplarily done for the Hamburg District Bergedorf (155 km2). The result shows that approximately 10,000 Mg/a of grass and lawn clippings could theoretically be made available. By laboratory investigations in batch tests the theoretical biogas potentials of selected grass and lawn substrates were determined. A statement about the suitability of the substrates for anaerobic digestion is made in this paper. The biogas potentials are between 325 and 720 standardized l per kg organic dry matter (l/kg ODM), depending on the sampling location, mowing time, grass species etc. For example, the biogas potentials for clippings from the dikes were in a range comparable with corn silage between 420 to 700 l/kg ODM. Additionally the problem of seasonal accumulation of grass biomass including the influence of storage on the initial material is considered in this paper. Keywords: grass, lawn, digestion, biogas potential.

Keywords

grass, lawn, digestion, biogas potential