Use of biogas: what are the pros and cons?

What is biogas and how can it be used

Biogas is a combustible mixture of gasses consisting mainly of methane (CH4) and carbon dioxide (CO). It is formed by the anaerobic bacterial decomposition of organic compounds such as sludge, agricultural or livestock biomass, plant by-products, and organic waste. The transformation process takes place in the absence of oxygen: the gasses formed are the waste products of the respiration of decomposing microorganisms.

The future role of biogas in sustainable energy supply is both distinct and flexible, as it can be used as a renewable source of electricity and heat when needed or can be stored. In addition, it is suitable for a variety of applications: it can be used directly for cooking and lighting, for combined heat and power generation, or to make both biomethane and biodiesel. 

According to experts, its increased use will help reduce the use of fossil fuels and thus reduce CO2 emissions. Thus, although estimated values vary between studies, the potential for producing biogas from biomass is enormous.

Biogas vs natural gas: what is the difference?

Natural gas is a naturally gaseous hydrocarbon mixture that forms beneath the earth's surface and is composed of 97-98% methane and the remaining 2-3% other numerous gasses such as nitrogen, helium, methane, carbon dioxide and hydrogen sulfide.

Compared to biogas, with which it is often confused, natural gas does have a similar composition but a very different origin and residual CO2 emission (35 percent versus 1 percent for biogas). In fact, to be extracted, it requires drilling, thus very high infrastructure costs. In addition, its combustion results in the production of a large amount of carbon dioxide that adversely affects the greenhouse effect, although in much smaller quantities than traditional fossil fuels such as coal and oil.

Advantages of biogas and its limitations

Worldwide interest in renewable energy sources is picking up: biogas production is steadily growing, and more and more people are deciding to install biogas production plants. In fact, there are numerous advantages of its use:

• It is a renewable energy source. Today's global energy supply depends heavily on fossil sources such as crude oil, lignite, hard coal, and natural gas.  These are nonrenewable resources, whose reserves are depleted much faster than those that are newly formed. Unlike fossil fuels, biogas from biomass is permanently renewable.

• Its production offers the possibility of additional income for the farmers involved. The production of feedstock in combination with the operation of biogas plants makes biogas technologies economically attractive to farmers and provides them with additional income, enabling them to acquire a new and important social function as energy suppliers and waste treatment operators.

• It contributes to the reduction of waste and disposal costs. One of the main advantages of biogas production is the ability to turn waste into a valuable resource by using it as a substrate for anaerobic digestion. Biogas production is an excellent way to comply with national and European regulations, which are always more restrictive in this area, and to use organic biomass from the agricultural, livestock and agribusiness sectors.

• It implies less water use. Compared with other biofuels, biogas also has some advantages. One of these is that the anaerobic digestion process requires less amount of process water.

• Allows the reduction of dependence on imported fossil fuels. Italy is heavily dependent on fossil energy imports from fossil-rich regions such as Russia, Africa, and the Middle East. The development and implementation of renewable energy systems, such as biogas from anaerobic digestion, based on domestic and regional biomass resources, allows for increased domestic energy supply and decreased dependence on imported fuels.

• Enables job creation. Production of biogas from anaerobic digestion requires manpower for production, collection and transportation of raw materials from anaerobic digestion, manufacture of technical equipment, construction, operation and maintenance of biogas plants. 

• A biogas plant also provides an excellent fertilizer. A biogas plant not only provides energy, but the digested substrate, usually called digestate, is a valuable soil fertilizer, rich in nitrogen, phosphorus, potassium and micronutrients, which can be applied to soils with the usual liquid manure application equipment. 

There are also some limitations to biogas technology: 

• An optimum temperature of about 37°C is required for anaerobic digestion: therefore, in cold climate areas, digesters require thermal energy to maintain a constant supply of biogas.

• Industrial biogas plants make sense only where feedstocks are abundant, so for companies that have plant waste, such as food waste and manure, in large quantities. 

• Building space of at least 2 ÷ 3 hectares is required for plant construction, so biogas generation is much more suitable for rural and suburban areas.

• Further technological advances are needed to simplify the process and make it abundant and low-cost. 

• Ammonia and hydrogen sulfide are present in biogas from anaerobic digestion, which can cause the production of unpleasant and persistent odors. As a solution to this problem, Idro Group has devised special filters that can purify the biogas.

Biogas plants built by Idro Group

In general, biogas plants and systems turn the cost of managing biomass and/or waste into a revenue opportunity for farms, livestock farms, dairies, and industries. Converting waste into electricity, heat or vehicle fuel provides a renewable energy source that can reduce dependence on foreign oil imports, reduce greenhouse gas emissions, improve environmental quality and increase local jobs. Biogas systems also provide an opportunity to recycle production waste, reducing the need for petrochemical and mining fertilizers. 

Idro Group specializes in the design and construction of biogas plants for energy creation and environmental protection; it can also create customized solutions to meet any specific customer requirements.

If you would like more information about biogas plants or if you would like to schedule a cognitive meeting with Idro Group staff, please fill out the form in the contact section. We will get back to you as soon as possible!