Advantages of biogas technologies

The generation and usage of biogas from anaerobic digestion and landfill gas ensures environmental and socio-economic benefits for the country as well as for the farmers which take part in it. Local biogas production increases local economic opportunities, provides new workplaces in rural regions and stimulates purchasing power. It is beneficial to living standards and promotes economic and social development. (Seadi et al. 2008)

Biogas utilization has the following benefits for the society:

• greenhouse gas emissions reduction and global warming mitigation,

• increase of independence on imported fossil fuels,

• promotion of European Union energy and environmental goals,

• waste reduction,

• job creation,

• flexible and efficient end usage of biogas,

• low water needs. (Seadi et al. 2008)

These benefits are discussed in more detail below. The global energy generation depends on fossil fuels such as crude oil, lignite, hard coal, and natural gas. During the millions of years, remains of plants and animals have been slowly decomposed and formed fossil fuels in the lithosphere. That is why fossil fuels are nonrenewable resources and their amount deplets faster than new ones come into being. (Seadi et al. 2008)

The World’s economy depends a lot on crude oil. There are discussions among scientists on how long crude oil will be available, and according to recent publications, the “peak oil production” has already been passed. (Seadi et al. 2008) Figure 8 illustrates the scenario of World oil production and “peak oil” among different regions and decades.

Figure 8. The scenario of World oil production and “peak oil” (Seadi et al. 2008).

As opposed to fossil fuels, biogas from anaerobic digestion and landfill gas are renewable, as they are generated from biomass and waste. Biogases can not only enhance the energy balance of a region but also make a vital contribution to the conservation of the natural resources and to nature protection. (Seadi et al. 2008)

The next benefit is greenhouse gas emissions reduction and global warming mitigation.

Usage of fossil fuels converts carbon, which has been kept in the lithosphere and delivers it as CO2 into the atmosphere. An increase of the current carbon dioxide concentration is the major reason of climate change because CO2 is a greenhouse gas. During biogas utilization, carbon dioxide also releases. Comparing to fossil fuels, carbon in biogas was lately taken up from the atmosphere by the photosynthetic process of the plants. Thus, the biogas carbon cycle is closed in a short period of time. Due to biogas generation, the concentration of methane and nitrous oxides in the atmosphere is also reduced. In the future, when biogas replaces fossil fuels, a decrease of emissions of carbon dioxide, methane, and nitrous oxides

into the atmosphere will take place, and it will contribute mitigation of global warming.

(Seadi et al. 2008)

Biogas utilization increases independence on imported fossil fuels. Fossil fuels are limited sources, located in several geographical regions of the planet. For the countries with a lack of fossil fuels, this creates a constant and insecure position of dependence on energy imports.

For example, most of the countries in Europe are strongly dependent on energy and fossil fuels import. For wide development and implementation of renewable energy systems, including biogas from anaerobic digestion and landfill gas, national and regional biomass sources and wastes are considered as basic resources, and they will guarantee the security of energy supply and improve local independence on energy import. (Seadi et al. 2008)

The next benefit is the promotion of European Union energy and environmental goals.

Prevention of climate change is one of the main targets of the European energy and environmental policies. The European aims of increasing renewable energy generation, reducing GHG emissions and applying smart waste treatment are based on the agreement of the European Union member states to promote correct activities to reach them. The generation and usage of biogas is essential in order to ensure the realization of all three targets at the same time. (Seadi et al. 2008)

Waste reduction is an important aspect of the modern society. One of the prime benefits of biogas generation is its capability to convert waste into a useful resource, by using it as a substrate for anaerobic processes. Many countries in the world have problems connected with the excess production of organic waste. Biogas generation is a good solution for compliance with more and more restrictive European waste management regulations. Biogas production also helps to reduce the waste amount and costs for waste disposal. (Seadi et al.

2008)

The last but not least benefits of biogas for the society are job creation, flexible and efficient end usage of biogas and low water needs. Generation of biogas needs labor force for maintaining all the functions of the biogas plants. It means that the growth of a national biogas sector helps to establish new plants, increases the quality of life in rural areas and creates new workplaces. Biogas is a flexible energy material, it can be utilized in various

applications. Biogas can be easily used for cooking and lighting, but in the present time biogas is utilized commonly in CHP units, as fuel for vehicles or fuel cells or it is upgraded and fed into natural gas grids. Even comparing to other biofuels, biogas has several benefits.

One of them is that the biogas production requires less volume of process water. This is an essential characteristic related to the prospective future water shortages in the planet. (Seadi et al. 2008)

In addition to all advantages listed above, biogas can bring the following benefits to involved farmers:

• carbon credits for reduction of methane emissions or renewable energy tariffs,

• additional income from electricity and heat generation when fed into the grid,

• digestate can be used as a soil fertilizer,

• closed nutrient cycle,

• possibility to use various feedstock,

• reduced odors and flies,

• veterinary safety. (Seadi et al. 2008)

One of the most valuable benefits for farmers is a possibility to have an additional income and special renewable energy tariffs. Production and utilization of biogas on plants makes these technologies economically feasible for farmers and ensures them additional income.

The farmers become also energy suppliers and waste treatment operators. (Seadi et al. 2008)

Digestate is a perfect soil fertilizer, which can be used in farms. Biogas plants are not only a provider of energy but also a digested substrate. It is rich in nitrogen, phosphorus, potassium, and micronutrients. Digestate can be used on soils with the technics for using liquid manure.

When comparing to raw animal manure, digestate has higher fertilizer efficiency due to higher homogeneity and nutrient existence, also lower carbon-to-nitrogen ratio, and noticeably reduced odors. Low carbon-to-nitrogen ratio means that digestate has a better short term N-fertilization value. (Seadi et al. 2008)

The third benefit for the farmers is the closed nutrient and carbon cycle. Methane is utilized for energy generation and the carbon dioxide is released to the atmosphere and re-uptaken

by plants during photosynthesis process. Biogas generation can be successfully integrated into common and organic farming, where it is possible to use digestate to replace chemical fertilizers, which were generated with consumption of large volumes of fossil power. (Seadi et al. 2008)

The next benefit of biogas for farmers is the flexibility to use various feedstock. A wide range of feedstock, agricultural and wastes, suitable for the biogas generation is shown in Table 4. One major benefit of biogas generation is the possibility to utilize wet biomass as feedstock, it has a moisture content higher than 60 – 70 percent. A lot of different energy crops such as grains, maize, and rapeseed, has been utilized as feedstock for generation of biogas in Germany and Austria. As well as energy crops, all types of agricultural residues, which cannot be used as food or results from unfavorable growing and weather conditions, can be utilized to generate biogas and fertilizer. Animal by-products, which are not good for human usage, can also be utilized for biogas production. (Seadi et al. 2008)

Table 4. Biogas feedstocks (European Biogas Association 2009).

Agriculture Waste streams

Manure Landfill

Energy crops, catch crops Sewage sludge

Landscape management Municipal solid waste

Grass Food waste

Other by-products Other waste

Reduction of odors and flies is also a major benefit. Storage and usage of animal liquid manure and municipal solid waste are responsible for strong, unpleasant odors and attract flies. Anaerobic digestion and landfill gas production reduce unpleasant odors by up to 80 percent. Digestate has almost no odor and remaining ammonia odors vanish into space quickly after application digestate as fertilizer. (Seadi et al. 2008)

Veterinary safety is also important. It has been proven, that the application of digestate as fertilizer, compared to untreated manure and slurries, can be beneficial for maintaining veterinary safety. To be suitable for utilization as fertilizer, digestate has to go through a special sanitation process. The goal of sanitation process is to deactivate pathogens and weed seeds and to avert diseases transmission. (Seadi et al. 2008)