Large biogas digesters at Zoomlion
What is biogas technology?
Biogas technology is the treatment of organic waste under anaerobic (air-free) condition. In practice, treatment is carried out in two main forms: wet and dry digestion. In wet digestion, the water content is at least three-quarters of the weight of the waste. In contrast, water content is less than a quarter of the feed weight for dry fermentation.
The treatment is carried out by bacteria in series of processes, resulting in formation of digested slurry (or digestate) and biogas. Biogas is a gaseous fuel that burns with a blue flame just like LPG.
Biogas digesters
The digester is the air-tight structure in which waste is treated. It is typically made of concrete, brick, steel, plastic, or fiberglass. Simple digesters may have volumes as low as six cubic meters while advanced ones may range from several hundreds to thousands of cubic meters.
Organic waste for biogas production
Many waste materials are suitable for treatment using biogas digesters. Notable materials include human excrement, animal (pig, cattle, poultry, etc.) manure, food waste, agro-industrial waste and wastewater, and agricultural residues. Concurrent decomposition (co-digestion) of different wastes can be carried out, resulting in high biogas production.
Biogas uses
Biogas can replace firewood, charcoal or LPG as cooking fuel. In industry, it can be used to generate steam for process heating or power generation.
In animal farms or slaughterhouses, biogas can be used to refrigerate animal products. When industries invest in biogas plants, they benefit from energy savings, reduced cost of waste treatment, and improved image.
Biomethane
When carbon dioxide in biogas is removed, biomethane is produced. Biomethane can be bottled and sold just like LPG. Biomethane is also used as automobile fuel, providing benefits such as lower emissions and noise compared to liquid fossil fuels.
The digested slurry (biofertilizer)
The digested slurry is rich in plant nutrients. Depending on the requirements of the owner (farm, company, et.), the slurry may be applied directly as organic fertiliser, used in composting or processed into solid fertilizer and packaged for sale. It is also used in fish farming as feed supplement.
History of biogas in Ghana
Biogas was recognised as an appropriate technology for rural development as far back as 1960 but was given much attention in the 80s and 90s, where government and donor agencies such as GIZ and UNDP sponsored capacity building of several engineers and artisans. Some household and community-based plants were installed to serve as training and demonstration projects.
For instance, in Appolonia, biogas plants were installed by the Ministry of Energy from 1988-1992, enabling that rural community to enjoy electricity for several years. Biogas plants were also built in hospitals, slaughterhouses, schools and farms. Presently, private companies rely on the ability of biogas digesters to treat waste as a marketing tool.
How biogas contributes to sustainable development in Ghana
Biogas technology is a proven technology and can become a key path to national development. Through biogas technology, a waste disposal problem can be turned into an income generating one.
Sanitation
Biogas digesters control odour and improve waste handling since digestion conditions destroy most pathogens and worms. The digesters also prevent seepage and thus protect underground water.
Energy
The potential to produce biogas for productive uses is high and promising in Ghana. Biogas can be used to displace firewood, charcoal or LPG both in the home and industry, resulting in fuel savings. Large scale use of biogas will boost national energy security via displacement of fossil-based fuels.
Agriculture
The use of biofertilizer in farming improves soil structure and increases harvest. Local farmers can save money meant for inorganic fertilizer while imports are reduced.
Other benefits
Installation of biogas plants create jobs at local and national levels through design, supply of materials, construction, and fabrication of appliances. Jobs are also created in processing and distribution of biofertilizer. If biogas is used to replace firewood, drudgery and indoor air pollution are reduced, and women’s heath are improved.
Case studies: treatment of municipal waste
There are several case studies where biogas systems have been used to solve problems with municipal waste.
Zoomlion faecal waste treatment plants
Biogas plants are key components of modern faecal treatment plants established by Zoomlion at Lavender Hill, Ajin Kotoku and Mudor, all in Accra. Before the investment, liquid waste from some parts of Accra was damped untreated in the sea, causing sea pollution which in turn affected fishing and tourism, among others. The plants treat about 5000 m3 of liquid waste daily, producing green electricity and organic fertiliser, which is made available to local farmers. Due to Zoomlion’s investment under PPP with government, Accra’s image has improved considerably in liquid waste management.
Safisana
At Ashaiman, faecal, market and other waste are treated using biogas plants managed by Safisana. The effluent is processed into liquid and solid forms which are used for irrigation and farming respectively. The biogas is used to generate electricity and fed to the national grid.
Industrial waste
Biogas systems are also used to treat various industrial waste and wastewater, including palm oil mill effluent (GOPDC, Kwae), brewery wastewater (Guinnes Ghana, Kumasi), and fruit waste (HPW Fresh & Dry Ltd., Adeiso).
Challenges
While substantial progress has been made in solar, the same cannot be said of biogas. Support to biogas initiatives has been unencouraging. Biogas companies operate with limited support – capacity building, promotion, credit, end-user financing, etc. Biogas digesters are costly mainly due to high cost of materials and lack of economy of scale. This has dwindled the industry since many households, farms, institutions and companies cannot afford biogas digesters.
Way forward
Ghana’s renewable energy (RE) law calls for 10% penetration of RE in total power generation by 2020. Unfortunately, RE currently makes about 1% of generation. Recognising the situation, the Vice President Dr. Mahamudu Bawumia, recently averred that government would not endorse new thermal plants and would rather institute measures to promote RE. Government should be commended for this positive decision which could become a major path to attainment of sustainable development goals.
It is feasible to generate a fair share of power from biogas if an enabling environment is created. Biogas needs to be promoted in promising sectors in a coordinated manner, with financial incentives (concessionary loans, tax holidays, etc.) made available to private companies and developers for grid-connected biogas power projects. The RE fund established under the RE Law should be expanded and accessible to private developers in RE business.
It is also necessary to simplify processes for acquiring permits for grid-connected biogas power projects, with ECG mandated to make prompt payment for power fed to grid. Moreover, the EPA and local authorities must enforce laws against discharge of untreated waste into the environment.
There is also the need for government to expand existing arrangements with companies such as Zoomlion and Safisana, to enable replication of their treatment facilities in other parts of the country. Combining anaerobic digestion of municipal solid waste with source separation can effectively solve the waste disposal crisis in Ghana, yield may economic, environmental and social benefits. Processing of biofertilizer for agricultural purposes can be integrated into the Planting for Food and Jobs programme, and can boost food security in the country.
Awareness creation for actors in promising sectors for biogas should be intensified. R&D should be intensified to support development of local technology in new and low-cost digester models that can be more affordable. Consequently, the newly formed Biogas Association of Ghana (BAG) requires government assistance to promote the technology in the country.
