A Biogas generator set is a type of power generation unit that converts biogas into electrical energy, and its high-power generation efficiency and high cost-effectiveness make it a perfect power option for customers worldwide.
Let’s imagine there is a large-scale greenhouse near a large-scale breeding farm, a large amount of organic waste will be produced from them every day, and it would be wasteful to just throw the organic waste away and it’s inefficient to simply return it into the farmland. How can we maximize the renewable use of resources, to achieve the double savings of resources and energy? What technical solution is there to utilize the waste resources of the two farms and turn their waste into something of value?
We know that livestock farms produce a large number of livestock manure every day, and the conventional disposal is to send the manure directly to the farmland, which is simple but inefficient. The direct discharge of faecal pollution leads to a serious waste of resources and poses a threat to the environment; while vegetable waste and organic wastes in greenhouses are thrown away or burned directly, resulting in a great waste of resources. So the question is, what are the alternative methods of disposing of natural waste?
Anaerobic fermentation technology
We can establish a collection and storage centre to house wastes such as livestock manure, and vegetable waste for centralised treatment in anaerobic fermentation equipment. The waste is mixed with anaerobic fermentation microbial strains and fermented in a low oxygen and constant temperature environment to produce products such as biogas, biogas slurry, and biogas residue. After treatment, biogas slurry and biogas residue can be returned to the field for reuse as organic fertilizer.
Figure1
Biogas slurry and biogas residue have achieved resource reuse accreditation, but how should we deal with these combustible high-quality biogas options?
Well, the biogas that has just been transported from the previous anaerobic fermentation stage has high humidity, impurities, and corrosive components such as H2S (Hydrogen Sulphide). Therefore, the biogas will be purified first via pre-treatment processes such as filtration, cold drying, and pressurization, then transported through pipelines to the desulfurization device for biogas desulfurization.
This purified biogas can be utilized in many ways, for example, if the surrounding users have a certain amount of demand for electricity and heat, an option for these users is to pursue a biogas co-generation solution. The generator unit burns biogas to generate electricity, which directly meets the electricity needs of the breeding farms and greenhouses, and the excess electricity can also be sold to the public power grid to achieve economic benefits. When the biogas generator unit operates, it also generates a large amount of heat with the temperature from the exhaust gas able to reach up to 400 ℃, but If it is directly discharged, it not only pollutes the environment but also wastes resources greatly. We can use a heat exchanger to make full use of the exhaust heat and supply it to the surrounding heat users, the heat produced can also be used in a heat exchanger, which is an optional extra, for users to use. For a heat exchanger, there are two large heat consumers in this application scenario, one is the anaerobic fermentation equipment, which needs constant temperature to maintain the activity of anaerobic bacteria; the other is that the greenhouse needs a lot of heat to keep the greenhouse warm. We can directly use the waste heat generated by the generator set to heat and preserve the anaerobic equipment and the greenhouse, so that the waste heat can be completely consumed, saving energy and improving economic benefits.
A biogas generator set is one of the main options for customers considering a cogeneration solution, with many models and brands available throughout the industry. The biogas generator set portfolio from PowerLink Company is relatively comprehensive. If the hourly biogas production is within 30m3, there is PowerLink's ACG series biogas cogeneration units (10kw-50kw); When the biogas volume is between 30 and 200m3, we can choose GX series units (50kw-500kw); and When the biogas volume is ≥ 200m3/h, we can choose the TCG series generator set (600-2000kW).
Figure2
How can biogas combustion products be utilised?
In addition to recycling the combustion heat for greenhouses, we can also use CO2 generated by combustion of biogas from the genset to fertilize vegetables within the greenhouse.
CO2 Application Principles
CO2 is an essential nutrient for crop growth and the main source of carbon for crops. Through photosynthesis, crops absorb CO2 from the air, forming metabolic products such as carbohydrates and proteins, and within a certain concentration range, CO2 is positively correlated with vegetable yield. The suitable CO2 concentration for crop growth is 0.11%~0.13%, while the CO2 content in the air is about 0.03%. In a greenhouse, the CO2 concentration of crops during the peak period of photosynthesis is only 0.02%, which is far from meeting the needs of crop growth. Biogas generally contains 30% to 40% CO2 and 50% to 70% methane. Methane combustion can generate a large amount of CO2 and release a large amount of thermal energy. The CO2 and heat energy can be sent to the greenhouse to increase the CO2 concentration and temperature in the greenhouse and effectively promote vegetable production.
Conclusion
The biogas generator unit is an important energy conversion device in the biogas cogeneration solution. The reuse of agricultural waste has saved resources and energy and has certain economic value, and provides the following options for customers as well:
1) Centralized treatment of organic waste is beneficial for environmental protection.
2) After anaerobic fermentation, the organic waste produced by the breeding farm and greenhouse, can be reused as organic fertilizer after treatment, realising the recycling and saving of resources.
3) After being burned by a power generation unit, biogas can generate a large amount of electricity and heat energy. The electricity can be used for its own use, and the excess electricity can be sold to the public power grid, while the heat energy can be used for anaerobic equipment and greenhouse insulation, achieving joint utilisation of heat and electricity, saving energy and greatly increasing the economic benefits of the customers.
4) CO2 generated after biogas combustion is sent to the greenhouse, which speeds up the photosynthesis of agricultural and vegetable products, saves fertilizer resources and reduces carbon emissions, which is conducive to environmental protection.