Using aquatic plant biomass from de-weeding in biogas processes\u2014an economically viable option?

Carsten Herbes,Sandra Roth,Markus Röhl,Vasco Brummer

doi:10.1186/s13705-018-0163-2

Carsten Herbes, Sandra Roth + Show 2 more

Open Access

https://doi.org/10.1186/s13705-018-0163-2

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Abstract

BackgroundLandscape maintenance in Germany today requires regular and extensive de-weeding of waterways, mostly to ensure water runoff and provide flood protection. The costs for this maintenance are high, and the harvested biomass goes to waste.MethodsWe evaluated the economic feasibility of using water plant biomass as a substrate in biogas generation. We set up a plausible supply chain, used it to calculate the costs of using aquatic water biomass as a seasonal feedstock to generate biogas, and compared it against maize silage, a standard biogas substrate. We also calculated the costs of using the aquatic biomass mixed with straw silage.ResultsAlthough subject to estimation errors, our results do show that it is economically feasible to use water plants as a seasonal feedstock in a biogas plant, even in markets where their disposal yields only moderate gate fees. Ensiling water plants with straw, however, incurs the added high price of straw and thus only yields a positive financial result if gate fees for water plant disposal are very high.ConclusionsWater plant biomass need not remain an unwelcome by-product of de-weeding waterways. The funds for its costly disposal can be redirected to the biomass supply chain and support the profitable use of aquatic biomass as a seasonal feedstock in biogas plants. However, the legal status of material from de-weeding needs to be clarified before biogas operators can act. Further development of technology for harvesting aquatic biomass is also called for.

Highlights

Landscape maintenance in Germany today requires regular and extensive de-weeding of waterways, mostly to ensure water runoff and provide flood protection
Supply-chain cost model To assess the economic feasibility of using aquatic biomass as a replacement for maize silage in biogas production, we modeled a 500 kW biogas plant based on energy crops, a very common plant configuration in Germany [29]
While aquatic macrophyte biomass from de-weeding of rivers and lakes can be used in many ways, our focus is on its use as a biogas substrate

Summary

Introduction

Landscape maintenance in Germany today requires regular and extensive de-weeding of waterways, mostly to ensure water runoff and provide flood protection The costs for this maintenance are high, and the harvested biomass goes to waste. Due to special incentives in the German Renewable Energy Act (REA), biogas plants in Germany use energy These efforts come at a time when the growth of water plants has become a costly problem, as operators of waterways face costs for de-weeding and disposing of aquatic biomass, much of it from the Elodea species (waterweeds) [5, 6]. Herbes et al Energy, Sustainability and Society (2018) 8:21 macrophytes (plants large enough to be seen by the naked eye) has swollen in volume Many of these plants, the so-called neophytes, are not originally domestic, so they are not well regulated by the local ecosystem. To find that local stakeholders, such as lake owners and municipalities, feel compelled to have the waterways cleared and the biomass taken to a service company such as a composting plant for disposal, both of which incur high costs

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