Environment

The production of biogas is a good idea for society in general, but also for the individual farmer, because:

• It produces renewable energy
• The farmer gets a better fertilizer from livestock manure
• Odor nuisances are limited
• The environment is saved from emissions of greenhouse gases
• The environment is saved from discharges of nutrients
• Organic waste is utilized and contributes to recycling

The physical and chemical change that occurs with the slurry in the biogas reactor gives a changed fertilizer effect in the field. The most significant change is the increase in the content of plant-available ammonium nitrogen. This is an advantage, as it is primarily the ammonium nitrogen that the plants can utilize. By using the degassed biomass as fertilizer, there is therefore the possibility of a higher harvest yield and a saving on the purchase of nitrogen in commercial fertilizer.

The thin and easy-flowing degassed slurry penetrates the soil relatively quickly. It helps to reduce the risk of ammonia evaporation.

When slurry is degassed, a number of substances which are always in the slurry are broken down. When using degassed slurry, the odor nuisance that may be associated with the application is reduced.

The risk of infection is reduced by processing the livestock manure in a biogas plant. The relatively long residence time at high heat reduces any infectious germs in the biogas reactor. If necessary, sanitization can be established at the biogas plant.

Society

In connection with the establishment of biogas plants, increased employment is typically created in an area. Especially in the establishment phase, local craftsmen can benefit. After establishment, an effort must be made in connection with operation and maintenance of the facility.

The local community can be proud of contributing to the solution of society-created climate and environmental problems and at the same time contributing to the production of local renewable energy.

In biogas plants, significant volumes of residues from agriculture, households and industry are digested, ensuring the recycling and reuse of the content of nutrients as fertilizer. With an intelligent use of biogas, these can be used to ensure the recirculation of phosphorus, which is a limited resource.

Biogas production has the potential to make a substantial contribution towards EU climate target for 2030.

The net climate impact of biogas exceeds the CO2savings from substituting fossil fuels.

Not only does biogas substitute fossil fuels, but it also reduces the carbon footprint from methane emissions during agricultural manure storage. However, biogas production also has a climate impact in the form of methane loss, energy consumption, and transportation of biomass and manure.

Proper management of the stables, combined with biogas, can significantly reduce the climate impact of livestock manure.

General Recommendations for the Mitigation of Environmental Impacts

Biogas production from manure and agricultural residues is widely recognized as a sustainable practice. The produced biogas can be used to generate both heat and electricity through combined heat and power (CHP) systems, or upgraded to biomethane for direct use as a renewable substitute to natural gas. However, despite the potential of these biofuels as green solutions, their overall production chain contains critical environmental hotspots that should be thoroughly examined.

To better understand the environmental outcomes of biomethane production, it is important to evaluate its environmental performance throughout its entire life cycle. By applying the Life Cycle Assessment (LCA) methodology, all environmental impacts linked to biomethane production are quantified and grouped into various representative categories. Thus, aggregated environmental factors such as Global Warming Potential (GWP), Terrestrial Acidification Potential (AP) and Freshwater Eutrophication Potential (EP) offer valuable insights into all impacts associated with climate change, soil integrity, and aquatic ecosystems, respectively.

Global Warming Potential (GWP)

The GWP impact category evaluates the potential contribution of a product or process to climate change, by quantifying all produced greenhouse gas (GHGs) emissions such as carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O). These gases are converted based on their heat trapping ability compared to CO₂, leading to the utilized metric unit of kg CO₂eq. The most common GHG emission sources in a biomethane production plant, alongside some reflective mitigation strategies are presented in the following table.

Terrestrial Acidification Potential (AP)

The AP impact category measures the capacity of acidifying substances, such as sulfur dioxide (SO₂), nitrogen oxides (NOₓ) and ammonia (NH₃) to affect the pH of soil, significantly reducing its quality. All the aforementioned compounds are converted based on their acidifying potential compared to SO₂, leading to the utilized metric unit of kg SO₂eq. Emission sources linked to AP in a biomethane plant and mitigation strategies are shown below.

Freshwater Eutrophication Potential (EP)

The EP impact category evaluates the potential of unregulated nutrient discharge, like phosphates (PO₄³–) and nitrates (NO₃–), into water bodies. This nutrient release causes excessive algal blooms that deplete oxygen levels and harm aquatic life. The following table lists key nutrient discharge sources and mitigation strategies.

The biogas plant tool