1 Introduction and objectives

Life Cycle Assessment of Biogas from Separated slurry

1.1 Background
1.2 Objectives and goal of the study
1.3 Organisation, Participants and Target Groups

1.1 Background

The Danish Environmental Protection Agency, in collaboration with different companies and organisations active in Denmark, initiated the preparation of a foundation for Life Cycle Assessment (LCA) for slurry management technologies. As a result, a recent LCA report was released assessing five different scenarios of slurry management (including a reference scenario for both fattening pigs and dairy cows slurry management), highlighting the environmental consequences and hot spots of these slurry management scenarios.

The present study represents a continuation of this foundation and build on the same reference scenarios. However, the emphasis of the present study is on different biogas production scenarios. In fact, anaerobic digestion of animal slurry has many acknowledged benefits such as: the production of a biogas rich in methane that can be used as a renewable energy source, mitigations effect on greenhouse gas and the production of an organic fertiliser having enhanced agronomic properties (as compared to raw slurry). In a high animal density country such as Denmark, anaerobic digestion therefore represents an interesting avenue not only for manure management, but also for renewable energy production, given the large quantities of slurry produced. Moreover, the target to use 40 % of all the slurry produced in Denmark for biogas production by 2020 has been announced many times, as well as the possibility to eventually use all manure produced in Denmark for biogas production. Currently, it is approximately only 5 % of the slurry that is digested for biogas production.

This project assesses four biogas production alternatives where, in all cases, slurry is the only input to the process. Although biogas produced exclusively from slurry input (i.e. without supplementary addition of easily degradable carbon) is not yet the most common practice in Denmark, it is likely to become an important alternative for the Danish panorama. This is due to the target to use more slurry for biogas production, but also to the limited availability of the C-source materials that are actually co-digested with the slurry.

As for the first publication of this LCA foundation initiative for slurry management technologies, the participating companies and organisations have agreed to put their own data, mass balances and emissions data at the disposal.

1.2 Objectives and goal of the study

The objective of the present study is to foster the on-going LCA foundation for Life Cycle Assessment of slurry management in Denmark (described in Wesnæs et al., 2009) by biogas production scenarios.

The outcomes of this study are:

A database containing Life Cycle data for the four selected biogas scenarios;
This report, containing the Life Cycle Assessment results and the interpretation of these for the four selected biogas scenarios;
Four detailed Annexes describing the calculation methodologies used, the data as well as the mass balances for the different process flows.

The goal of this study is the same as in the first part of this on-going LCA foundation for Life Cycle Assessment of slurry management in Denmark, i.e. to provide an answer to the following question:

“What are the environmental benefits and disadvantages of introducing this technology for slurry management?”

Therefore, all biogas scenarios established in this study will be compared to the reference slurry management scenario established in Wesnæs et al. (2009), i.e. using raw slurry as an organic fertiliser and spread it on land without any prior treatment.

The results of this study are intended for public disclosure and will be communicated to all participating companies and organisations. They are intended to provide a rigorous and documented support to decision making as regarding the implementation of the different biogas technologies presented in this study (as an alternative to the conventional slurry management).

1.3 Organisation, Participants and Target Groups

This study was commissioned by the Environmental Protection Agency of Denmark. The project was carried out in the period August 2009 - December 2009 for a budget corresponding to approximately 1½ month of fulltime work.

The steering committee for the study includes:

Peter H. Schaarup, Environmental Protection Agency of Denmark
Anton Rasmussen, Environmental Protection Agency of Denmark
Thomas Alstrup, FORA
Frank Rosager, Xergi A/S
Michael Støckler, Agro Business Park
Jesper Kløverpris, Novozymes
Thomas Schrøder, Novozymes
Gunnar Hald Mikkelsen, Samson-Agro A/S
Thorbjørn Machholm, Grundfos Management A/S
Jesper Ravn Lorenzen, Grundfos New Business A/S

This study could not have been performed without the significant contributions from:

Frank Rosager, Xergi A/S
Anders Peter Jensen, Xergi A/S
Henrik Vestergaard Laursen, Xergi A/S
Jesper Andersen, Xergi A/S

Furthermore, the authors would like to acknowledge the contributions from:

Karsten Buchhave, Bigadan
Birgir Norddahl, University of Southern Denmark
Teodorita Al Seadi, University of Southern Denmark
Martin Nørregaard Hansen, Agrotech, Institut for Jordbrugs- og Fødevareinnovation
Henrik B. Møller, Institut for Jordbrugsteknik
Lars Jørgen Pedersen, Green Farm Energy A/S

The study has been carried out by Lorie Hamelin, Marianne Wesnæs and Henrik Wenzel from the University of Southern Denmark in close collaboration with Bjørn Molt Petersen, Department of Agroecology and Environment, Faculty of Agricultural Sciences, Aarhus University.