Cofiring of biomass involves utilizing existing power generating plants that are fired with fossil fuel (generally coal), and displacing a small proportion of the fossil fuel with renewable biomass fuels. Cofiring of biomass with coal and other fossil fuels can provide a short-term, low-risk, low-cost option for producing renewable energy while simultaneously reducing the use of fossil fuels.
Biomass can typically provide between 3 and 15 percent of the input energy into the power plant. Cofiring of biomass has the major advantage of avoiding the construction of new, dedicated, biomass power plant. An existing power station is modified to accept the biomass resource and utilize it to produce a minor proportion of its electricity.
Cofiring of biomass may be implemented using different types and percentages of biomass in a range of combustion and gasification technologies. Most forms of biomass are suitable for cofiring. These include dedicated energy crops, urban wood waste and agricultural residues such as rice straw and rice husk.
The fuel preparation requirements, issues associated with combustion such as corrosion and fouling of boiler tubes, and characteristics of residual ash dictate the cofiring configuration appropriate for a particular plant and biomass resource. These configurations may be categorized into direct, indirect and parallel firing.
1. Direct Cofiring
This is the most common form of biomass cofiring involving direct cofiring of the biomass fuel and the primary fuel (generally coal) in the combustion chamber of the boiler. The cheapest and simplest form of direct cofiring for a pulverized coal power plant is through mixing prepared biomass and coal in the coal yard or on the coal conveyor belt, before the combined fuel is fed into the power station boiler.
2. Indirect Cofiring
If the biomass fuel has different attributes to the normal fossil fuel, then it may be prudent to partially segregate the biomass fuel rather than risk damage to the complete station.
For indirect cofiring, the ash of the biomass resource and the main fuel are kept separate from one another as the thermal conversion is partially carried out in separate processing plants. As indirect co-firing requires a separate biomass energy conversion plant, it has a relatively high investment cost compared with direct cofiring.
Parallel Firing
For parallel firing, totally separate combustion plants and boilers are used for the biomass resource and the coal-fired power plants. The steam produced is fed into the main power plant where it is upgraded to higher temperatures and pressures, to give resulting higher energy conversion efficiencies. This allows the use of problematic fuels with high alkali and chlorine contents (such as wheat straw) and the separation of the ashes.
South Africa is experiencing a mammoth energy crisis with its debt-laden national power utility, Eskom, being unable to meet the electricity needs of the nation. After extensive periods of load shedding in 2018 and again earlier this year, it is becoming increasingly important to find an alternative source of energy. According to Marko Nokkala, senior sales manager at VTT Technical Research Centre of Finland, South Africa is in the perfect position to utilize biomass as an alternative source of energy.
Things to Consider
Should South Africa choose to delve deeper into biomass energy production, there are a few things that need to be considered. At present, a lot of biomass (such as fruit and vegetables) is utilized as food. It will, therefore, be necessary to identify alternative biomass sources that are not typically used as food, so that a food shortage is never created in the process.
One alternative would be to use municipal solid waste from landfills and dumpsites as well as the wood waste from the very large and lucrative forestry industry in the country. It is also essential to keep in mind that an enormous amount of biomass will be needed to replace even a portion of the 90 million tons of coal that Eskom utilizes every year at its various power stations.
Potential Biomass Conversion Routes
There are a number of processing technologies that South Africans can utilize to turn their biomass into a sustainable energy source. Biochemical conversion involving technology such as anaerobic digestion and fermentation makes use of enzymes, microorganisms, and bacteria to breakdown the biomass into a variety of liquid or vaporous fuels.
Fermentation is especially suitable when the biomass waste boasts a high sugar or water content, as is the case with a variety of agricultural wastes. By placing some focus on microbial fermentation process development, a system can effectively be created that will allow for large-scale biofuel production. Other technologies to consider include thermal methods like co-firing, pyrolysis, and gasification.
Future of biomass energy in South Africa
Despite the various obstacles that may slow down the introduction of large-scale biomass energy production in the country, it still promises to be a viable solution to the pressing energy concern. Biomass energy production does not require any of the major infrastructures that Eskom is currently relying on.
Although the initial setup will require a substantial amount of electricity, running a biomass conversion plant will cost significantly less than a coal-powered power plant in the long run. With the unemployment rate hovering around 27.1% in South Africa at present, any jobs created through the implementation of biomass energy conversion will be of great benefit to the nation.
Conclusion
Without speedy intervention, South Africa may very soon be left in the dark. Although there are already a number of wind farms in operation in the country, the addition of biomass conversion facilities will undoubtedly be of great benefit to Africa’s southernmost country.
In recent years, the world has seen significant economic progress, which greatly relied on energy fueled by coal and petroleum among others. With the continuously growing demand for energy, it is a fact that these energy sources may be depleted in the near future. Apart from this, there are several other reasons why humankind already needs to find alternative energy sources.
Global Warming
It is a known fact that different manufacturing processes and human activities, such as using vehicles, cause pollution in the atmosphere by releasing carbon dioxide. Carbon dioxide traps heat in the earth, and this phenomenon is known as global warming. Global warming has several harmful impacts such as stronger and more frequent storms, as well as drought and heat waves. Renewable energy sources such as wind, solar, geothermal, hydroelectric, and biomass to name a few, all generate minimal global warming emissions.
Wind power, for instance, has the capability to supply energy with a significantly lower emission compared to burning coal for fuel. This is the reason why wind energyis more beneficial compared to carbon-intensive energy sources. Still, the emissions generated by wind power are even lower compared to other renewable energy sources such as solar, geothermal, and hydroelectric power sources. This makes a huge potential for wind power to sustain the world’s energy demands, while preserving the environment.
Public Health
It goes without saying that the pollution caused by burning coal and fuel not only has an environmental impact, but it also has a significant effect on public health. Various diseases and ailments can be attributed to pollution, which usually affects the respiratory tract. Contaminated water also causes various bacterial infections. Wind power, solar energy, and hydroelectric systems have the capability to generate electricity without emitting air pollutants.
Additionally, wind and solar energy sources do not need water to operate, thereby, eliminating the probability of polluting water resources. Clean air and water that is free from pollutants, will have a significant positive impact on public health.
Constant Energy Source
While coal and fossil fuels are on the threshold of depletion, renewable energy sources are inexhaustible. Wind can be a constant energy source and no matter how high the demand for energy will be, the wind will not be depleted. In the same manner, as long as the sun shines bright on earth, there will always be an abundant solar energy source.
Fast-moving water that can be translated into hydroelectric energy, the earth’s heat that can be converted into a geothermal power source, as well as abundant plant matter that can be used as biomass, can all be constantly replenished. These can never be fully exhausted no matter how great the energy demand will be. The utilization of a combination of each of these energy sources will prove to be even more beneficial. Additionally, with its continued use, there will no longer be a need for combustible energy sources.
Lower Energy Costs
The cost of electricity continues to be a burden on the earth’s greater population. The use of renewable energy sources to light up the earth is considerably cheaper and inexpensive compared to the cost of burning fossil fuels for electricity and other energy needs. Apart from a cheaper cost, renewable energy sources can help stabilize to cost of energy in the long run, with an unlimited supply being able to cater to greater demand. Don’t forget to obtain more information on the size of solar energy system you need for your home.
While it cannot be denied that setting up clean energy technologies comes with a cost, it can be noted that the cost of its operation is significantly lower. Conversely, the cost of coal and fossil fuels for energy consumption fluctuates over a wide range and is greatly affected by the economic and political conditions of its country of origin.
Economic Benefits
Fossil fuel technologies, often, revolve around the capitalistic market. Hence, the use of combustible fuels is often linked to unfavorable labor conditions, and even child labor and slavery. On the other hand, the use of renewable energy sources provides decent jobs, contributing to several economic benefits and aids in decarbonizing the future.
For instance, workers are needed to install and maintain solar panels. In the same manner, wind farms employ technicians for maintenance. Thus, jobs are created directly in parallel with the unit of energy produced. This means that more jobs will be produced if more renewable energy sources are utilized.
Reliability
Clean energy sources, specifically wind and solar power, are less susceptible to large-scale failures. The reason behind this is that both wind and solar power both employ distributed and modular systems. This means that electricity will not be totally cut off in instances of extreme weather conditions because the energy sources powering up the electricity is spread out over a wider geographical area. In the same manner, there will still be a continuous supply of energy even if certain equipment in the entire system is damaged because clean fuel technologies are made up of modules such as a number of individual wind turbines or solar panels.
With all the reasons to check out alternative energy sources, it still holds true that there remain several barriers that hinder the full implementation of renewable energy technologies. Some of these challenges are capital costs because of reliability misconceptions, as well as a difficult market entry due to an unequal playing field.
Because renewable energy sources are cheap to operate, the bulk of the expenses in its implementation is building the technology. Thereby, the rate of return for capitalists and investors in the market entails a longer waiting period. Adding to this barrier is the hidden political agenda that most governments need to overcome. Many governments offer grants to help with this growth and rate or return.
Economic progress and advancement in technology are not at all bad. On the contrary, it has brought forth a lot of benefits such as cures for ailments and diseases, resources for deep-sea or space explorations, as well as meaningful collaboration and communication. However, this progress came with a price, and unfortunately, it’s the world’s energy resources that are on the brink of exhaustion. Hence, mitigation has been already necessary and finding alternative energy sources is just one of the probable solutions.
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