Thermal Conversion of Biomass

A wide range of technologies exists to convert the energy stored in biomass to more useful forms of energy. These technologies can be classified according to the principal energy carrier produced in the conversion process. Carriers are in the form of heat, gas, liquid and/or solid products, depending on the extent to which oxygen is admitted to the conversion process (usually as air). The major methods of thermal conversion are combustion in excess air, gasification in reduced air, and pyrolysis in the absence of air.

Combustion

Conventional combustion technologies raise steam through the combustion of biomass. This steam may then be expanded through a conventional turbo-alternator to produce electricity. A number of combustion technology variants have been developed. Underfeed stokers are suitable for small scale boilers up to 6 MWth. Grate type boilers are widely deployed. They have relatively low investment costs, low operating costs and good operation at partial loads. However, they can have higher NOx emissions and decreased efficiencies due to the requirement of excess air, and they have lower efficiencies.

Fluidized bed combustors (FBC), which use a bed of hot inert material such as sand, are a more recent development. Bubbling FBCs are generally used at 10-30 MWth capacity, while Circulating FBCs are more applicable at larger scales. Advantages of FBCs are that they can tolerate a wider range of poor quality fuel, while emitting lower NOx levels.

Co-Firing

Co-firing or co-combustion of biomass wastes 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. Co-firing 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. Co-firing has the major advantage of avoiding the construction of new, dedicated, waste-to-energy power plant. Co-firing may be implemented using different types and percentages of wastes in a range of combustion and gasification technologies. Most forms of biomass wastes are suitable for co-firing. These include dedicated municipal solid wastes, wood waste and agricultural residues such as straw and husk.

Gasification

Gasification of biomass takes place in a restricted supply of oxygen and occurs through initial devolatilization of the biomass, combustion of the volatile material and char, and further reduction to produce a fuel gas rich in carbon monoxide and hydrogen. This combustible gas has a lower calorific value than natural gas but can still be used as fuel for boilers, for engines, and potentially for combustion turbines after cleaning the gas stream of tars and particulates. If gasifiers are ‘air blown’, atmospheric nitrogen dilutes the fuel gas to a level of 10-14 percent that of the calorific value of natural gas. Oxygen and steam blown gasifiers produce a gas with a somewhat higher calorific value. Pressurized gasifiers are under development to reduce the physical size of major equipment items.

A variety of gasification reactors have been developed over several decades. These include the smaller scale fixed bed updraft, downdraft and cross flow gasifiers, as well as fluidized bed gasifiers for larger applications. At the small scale, downdraft gasifiers are noted for their relatively low tar production, but are not suitable for fuels with low ash melting point (such as straw). They also require fuel moisture levels to be controlled within narrow levels.

Pyrolysis

Pyrolysis is the term given to the thermal degradation of wood in the absence of oxygen. It enables biomass to be converted to a combination of solid char, gas and a liquid bio-oil. Pyrolysis technologies are generally categorized as “fast” or “slow” according to the time taken for processing the feed into pyrolysis products. These products are generated in roughly equal proportions with slow pyrolysis. Using fast pyrolysis, bio-oil yield can be as high as 80 percent of the product on a dry fuel basis. Bio-oil can act as a liquid fuel or as a feedstock for chemical production. A range of bio-oil production processes are under development, including fluid bed reactors, ablative pyrolysis, entrained flow reactors, rotating cone reactors, and vacuum pyrolysis.

What is a Power Inverter and Why do I Need One?

Are you the owner of an RV, SUV, car, boat or other vehicle, and want to be able to watch TV, cook, or power a laptop onboard? If yes, you’ll be needing a power inverter. But what are they, and what do they do?

Read on to find out why you’ll need one to power your gadgets on the road…

What is a Power Inverter?

Basically, they are devices that turn your vehicle battery’s direct current (DC) into alternating current (AC) – the kind of electricity you have in outlets in your house, that are connected to the energy grid.

Having a power converter means you can plug in your appliances and devices, and power them like you would through an electricity outlet in a house.

In your car, you can get USB adaptors for your cigarette lighter so that you can charge your phone or plug in your satnav. But for larger gadgets and electronics with proper plugs, you’ll need an inverter.

Working of a Power Inverter

Like we said, they convert currents to a type safe for use in vehicles. Your vehicle’s battery voltage provides a current that powers its internal workings – you’ll need to know which voltage your vehicle’s battery uses to choose the correct inverter.

The current supplied by a battery sticks on one circuit, in one direction – where the name ‘direct current’ comes from.

However, to power your gadgets, you’ll need alternating current, as those electronics need more power to function than the DC can provide. They’re made to function with the high-voltage AC current supplied in homes.

Power inverters increase the DC voltage, change it to AC, then use it to power your devices. They amp up your battery’s voltage so you can play video games and use a kettle in your RV. Cool, huh?

Size Selection

These babies come in a variety of sizes – most commonly 1000, 3000 or 5000 watts.

It’s recommended that a 3000 watt inverter is the happy medium between inverter sizes and best choice to get. They’re not too small like the 1000, or too powerful and overcharged like the 5000. If you need a little extra boost, there are 3500 watt capacities available.

Find the best 3000 watt inverter for your vehicle by checking out the useful comparison guide by Solar Know How.

Modified or Pure Sine Wave Inverter?

Besides the sizing, there are two main types of inverter – the modified sine wave, and the pure sine wave.

So, what’s the difference, and which one will you need?

  • Modified Sine Wave: These tend to be cheaper, and less powerful. However, they’re good for most everyday electronics you will want to use, just not very large ones.
  • Pure Sine Wave: These are compatible with pretty much all electronics, gadgets, and appliances, and produce a powerful current most like the one supplied by the electric grid. These are the most common choice, because they’re more likely to be compatible with anything you need to plug in.

Power inverters are useful for charging on the road without having to cart around adaptors and large plugs

Other Features and Tips

  • Power inverters are especially useful if you are setting up a solar power system – they convert energy from the sun into electricity you can use to power your gadgets within your vehicle. This is renewable energy that isn’t a drain on your vehicle’s battery.
  • Power inverters aren’t just for vehicles – if you have a small cottage or outhouse, they’re very useful for setting up a small power source there.
  • Many (but not all) power inverters come with USB outlets, useful for charging on the road without having to cart around adaptors and large plugs. For ease of use, get one compatible with USB.
  • The best inverters have digital screens which show you how much energy has been consumed and information about battery voltage. It’s useful to know these things at a glance, so consider getting one that has a screen.
  • Modern inverters have been made to be extra-quiet, so you won’t be woken up by a noisy machine while trying to simultaneously get some sleep and charge your phone in your RV.

Biomethane – The Green Gas

Biomethane, also known as the green gas, is a well-known and well-proven source of clean energy, and is witnessing increasing demand worldwide, especially in European countries, as it is one of the most cost-effective and eco-friendly replacement for natural gas and diesel.

Advantages of Biomethane

The key advantage of biomethane is that it is less corrosive than biogas which makes it more flexible in its application than raw biogas. It can be injected directly into the existing natural gas grid leading to energy-efficient and cost-effective transport, besides allowing natural gas grid operators to persuade consumers to make a smooth transition to a renewable source of natural gas.

Biogas can be upgraded to biomethane and injected into the natural gas grid to substitute natural gas or can be compressed and fuelled via a pumping station at the place of production. Biomethane can be injected and distributed through the natural gas grid, after it has been compressed to the pipeline pressure.

The injected biomethane can be used at any ratio with natural gas as vehicle fuel. In many EU countries, the access to the gas grid is guaranteed for all biogas suppliers.

A major advantage of using natural gas grid for biomethane distribution is that the grid connects the production site of biomethane, which is usually in rural areas, with more densely populated areas. This enables biogas to reach new customers.

Storage of Biomethane

Biomethane can be converted either into liquefied biomethane (LBM) or compressed biomethane (CBM) in order to facilitate its long-term storage and transportation. LBM can be transported relatively easily and can be dispensed through LNG vehicles or CNG vehicles. Liquid biomethane is transported in the same manner as LNG, that is, via insulated tanker trucks designed for transportation of cryogenic liquids.

Biomethane can be stored as CBM to save space. The gas is stored in steel cylinders such as those typically used for storage of other commercial gases.

Applications of Biomethane

Biomethane can be used to generate electricity and heating from within smaller decentralized, or large centrally-located combined heat and power plants. It can be used by heating systems with a highly efficient fuel value, and employed as a regenerative power source in gas-powered vehicles.

Biomethane, as a transportation fuel, is most suitable for vehicles having engines that are based on natural gas (CNG or LNG). Once biogas is cleaned and upgraded to biomethane, it is virtually the same as natural gas.

Because biomethane has a lower energy density than NG, due to the high CO2 content, in some circumstances, changes to natural gas-based vehicle’s fuel injection system are required to use the biomethane effectively.

Bagasse-Based Cogeneration in Pakistan: Challenges and Opportunities

Considering the fact that Pakistan is among the world’s top-10 sugarcane producers, the potential of generating electricity from bagasse is huge.  Almost all the sugar mills in Pakistan have in-house plants for cogeneration but they are inefficient in the consumption of bagasse. If instead, high pressure boilers are installed then the production capacity can be significantly improved with more efficient utilization of bagasse.

However, due to several reasons; mostly due to financing issues, the sugar mill owners were not able to set up these plants. Only recently, after financial incentives have been offered and a tariff rate agreed upon between the government and mill owners, are these projects moving ahead.

The sugar mill owners are more than willing to supply excess electricity generated form the in-house power plants to the national grid but were not able to before, because they couldn’t reach an agreement with the government over tariff. The demand for higher tariff was justified because of large investments in setting up new boilers. It would also have saved precious foreign exchange which is spent on imported oil.

By estimating the CDM potential of cogeneration (or CHP) projects based on biofuels, getting financing for these projects would be easier. Renewable energy projects can be developed through Carbon Development Mechanism or any other carbon credit scheme for additional revenue.

Since bagasse is a clean fuel which emits very little carbon emissions it can be financed through Carbon Development Mechanism. One of the reasons high cogeneration power plants are difficult to implement is because of the high amount of costs associated. The payback period for the power plants is unknown which makes the investors reluctant to invest in the high cogeneration project. CDM financing can help improve the rate of return of the project.

Bagasse power plants generate Carbon Emission Reductions in 2 ways; one by replacing electricity produced from fossil fuels.  Secondly if not used as a fuel, it would be otherwise disposed off in an unsafe manner and the methane emissions present in biomass would pollute the environment far more than CO2 does.

Currently there are around 83 sugar mills in Pakistan producing about 3.5 million metric tons of sugar per annum with total crushing capacity 597900 TCD, which can produce approximately 3000 MW during crop season Although it may seem far-fetched at the moment, if the government starts to give more attention to  sugar industry biomass rather than coal, Pakistan can fulfill its energy needs without negative repercussions or damage to the environment.

However some sugar mills are opting to use coal as a secondary fuel since the crushing period of sugarcane lasts only 4 months in Pakistan. The plants would be using coal as the main fuel during the non-crushing season. The CDM effect is reduced with the use of coal. If a high cogeneration plant is using even 80% bagasse and 20% of coal then the CERs are almost nullified. If more than 20% coal is used then the CDM potential is completely lost because the emissions are increased. However some sugar mills are not moving ahead with coal as a secondary fuel because separate tariff rates have to be obtained for electricity generation if coal is being used in the mix which is not easily obtained.

Pakistan has huge untapped potential for bagasse-based power generation

One of the incentives being offered by the State Bank of Pakistan is that if a project qualifies as a renewable project it is eligible to get loan at 6% instead of 12%. However ones drawback is that, in order to qualify as a renewable project, CDM registration of a project is not taken into account.

Although Pakistan is on the right track by setting up high cogeneration power plants, the use of coal as a secondary fuel remains debatable.  The issue that remains to be addressed is that with such huge amounts of investment on these plants, how to use these plants efficiently during non-crushing period when bagasse is not available. It seems almost counter-productive to use coal on plants which are supposed to be based on biofuels.

Conclusion

With the demand for energy in Pakistan growing, the country is finally exploring alternatives to expand its power production. Pakistan has to rely largely on fossils for their energy needs since electricity generation from biomass energy sources is considered to be an expensive option despite abundance of natural resources. However by focusing on growing its alternate energy options such as bagasse-based cogeneration, the country will not only mitigate climate change but also tap the unharnessed energy potential of sugar industry biomass.

Biomass Energy in Nigeria: An Overview

biomass-sustainabilityOil and gas accounts for over 70% of energy consumed in Nigeria, according to the World Bank. Considering this dependency on fossil oil and possibility of it running out in the future, there should be an urgent intervention to look into other ways to generate energy in Nigeria. The world is moving away gradually from fossil oil and aligning towards sustainable energy resources to substitute conventional fuel, Nigeria should not be exempted from this movement. Biomass, a popular form of renewable energy, is considered as a credible and green alternative source of energy which many developed and developing countries have been maximizing to its potential.

Power generation and supply have been inadequate in Nigeria. This inadequacy of power limits human, commercial and industrial productivity and economic growth . What is the use of infrastructure without constant electricity? Even God created light first. Sustainable and constant supply of power should be one of the priority of government in nation development. Investing in biomass will cause an increase in the amount of power generated in Nigeria. Infact, biomass energy has the potential to resolve the energy crisis in the country in the not so distant future.

What is Biomass

The word biomass refers to organic matter (mainly plants) which acts as a source of sustainable and renewable energy. It is a renewable energy source because the plants can be replaced as oppose to the conventional fossil fuel which is not renewable. Biomass energy is a transferred energy from the sun; plants derives energy from the sun through photosynthesis which is further transferred through the food chain to animals’ bodies and their waste.

Biomass has the potential to provide an affordable and sustainable source of energy, while at the same time help in curbing the green house effect. In India the total biomass generation capacity is 8,700 MW according to U.S. of Commerce’s International Trade Administration, whereas the generating capacity in U.S. is 20,156  MW with 178 biomass power plants, according to Biomass Magazine.

Power Sector in Nigeria

Unfortunately, the total installed electricity capacity generated in Nigeria is 12,522MW, well below the current demand of 98,000MW . The actual output is about 3,800MW, resulting in a demand shortfall of 94,500MW throughout the country. As a result of this wide gap between demand and output, only 45% of Nigeria’s population has access to electricity. Renewable energy contributed 19% of total electricity generated in Nigeria out of which biomass contribution is infinitesimal.

Electricity generation for Nigeria’s grid is largely dominated by two sources; non-renewable thermal (natural gas and coal) and renewable (hydro). Nigeria depends on non-renewable energy despite its vast potential in renewable sources such as solar, wind, biomass and hydro. The total potential of these renewables is estimated at over 68,000MW, which is more than five times the current power output.

Biomass Resources in Nigeria

Biomass can come in different forms like wood and wood waste, agriculture produce and waste, solid waste.

Wood

Electricity can be generated with wood and wood product/waste(like sawdust) in modern day through cogeneration, gasification or pyrolysis.

Agriculture Residues

In Nigeria, agricultural residues are highly important sources of biomass fuels for both the domestic and industrial sectors. Availability of primary residues for energy application is usually low since collection is difficult and they have other uses as fertilizer, animal feed etc.

However secondary residues are usually available in relatively large quantities at the processing site and may be used as captive energy source for the same processing plant involving minimal transportation and handling cost.

Municipal Solid Waste

Back then in secondary school, I learnt that gas could be tapped from septic tank which could further be used for cooking.  Any organic waste (like animal waste, human waste) when decomposed by anaerobic microorganisms releases biogas which can be tapped and stored for either cooking or to generate electricity.

Biomass can be used to provide heat and electricity as well as biofuel and biogas for transport. There are enough biomass capacity to meet our demand for electricity and other purposes. From climatic point of view, there is a warm climate in Nigeria which is a good breeding ground for bacteria to grow and decompose the wastes. There are plant and animal growth all year round which in turn create waste and consequently produce biomass.

In November 2016, The Ebonyi State Government  took over  the United Nations Industrial Development Organization (UNIDO) demonstration biomass gasifier power plant located at the UNIDO Mini -industrial cluster in Ekwashi Ngbo in Ohaukwu Local Government Area of the State. The power plant is to generate 5.5 Megawatt energy using rice husk and other available waste materials available. More of these type of power plants and commitment are needed to utilize the potential of biomass fully.

Why Biomass Energy?

Since biomass makes use of waste to supply energy, it helps in waste management. It also has the potential to supply more energy (10 times) than the one produced from sun and wind. Biomass will lead to increase in revenue generation and conserves our foreign exchange. Increase in energy generation will yield more productivity for industries and the rate at which they are shutting down due to the fact that they spend more on power will be reduced to minimal.

Many local factories/companies will spring up and foreign investors will be eager to invest in Nigeria with little concern about power. Establishment of biopower plants will surely create more jobs and indirectly reduce the number of people living in poverty which is increasing everyday at an alarming rate.

Africa’s most populous country needs more than 10 times its current electricity output to guarantee supply for its 198 million people – nearly half of whom have no access at all, according to power minister Babatunde Fashola. Biomass energy potential in Nigeria is promising –  with heavy investment, stake holder cooperation and development of indigenous technologies. The deployment of large-scale biomass energy systems will not only significantly increase Nigeria’s electricity capacity but also ease power shortages in the country.

Renewable Energy in Refugee Camps

dabaab-refugee-campAccess to clean and affordable energy is a prerequisite for sustainable development of mankind, and refugees are no exception. Refugee camps across the world house more than 65 million people, and almost all refugee camps are plagued by fuel poverty. Needless to say, urgent measure are required to make camps livable and sustainable.

Rapid advancements in renewable energy technologies have made it possible to deploy such systems on various scales.  The scalability potential of renewable energy systems makes them well-suited for refugee camps, especially in conflict-afflicted areas of the Middle East, Asia and Africa.

Renewable energy in refugee camps can be made available in the form of solar energy, biomass energy and wind energy. Solar panels, solar cooking units, solar lanterns, biomass cookstoves and biogas plants are some of the popular renewable energy technologies that can improve living standards in refugee camps. It is important to focus on specific needs of refugees and customization of technology towards local conditions. For example, solar technologies are better understood than biogas systems in Jordan.

Solar Energy

Solar energy can provide long-term resilience to people living in refugee camps. With many camps effectively transformed into full-fledged towns and cities, it is essential to harness the power of sun to run these camps smoothly. Solar cookers, solar lanterns and solar water heaters are already being used in several refugee camps, and focus has now shifted to grid-connected solar power projects.

The 5MW Azraq solar project is the world’s first grid-connected renewable energy project to be established in a refugee camp. The project is being funded entirely by Ikea through the Brighter Lives for Refugees campaign. The program, now in its third year, seeks to improve the lives of refugees around the world by providing access to sustainable energy supplies.

Biomass Energy

Due to lack of land and resources, refugee camps puts tremendous pressure on natural vegetation, especially supply of fuel wood to camp-dwellers. Replacement of traditional stoves with efficient biomass-fired cook stoves can save as much as 80% of cooking fuel.

Instead of wood, it would be also be a good option to use agricultural wastes, like husk and straw. Another interesting proposition for refugee camps is to set up small-scale DIY biogas plants, based on human wastes and food residuals. The biogas produced can be used as a cooking medium as well as for power/heat generation.

Wind Energy

Small wind turbines can also play a key role in providing energy to dwellers of refugee camps. Such turbines are used for micro-generation and can provide power from 1kW to 300kW. Majority of small wind turbines are traditional horizontal axis wind turbines but vertical axis wind turbines are a growing type of wind turbine in the small wind market. Small wind turbines are usually mounted on a tower to raise them above any nearby obstacles, and can sited in refugee camps experiencing wind speeds of 4m/s or more.

Solar lights in Azraq Refugee Camp (Jordan)

Solar lights in Azraq Refugee Camp (Jordan)

Conclusions

Renewable energy systems have the potential to improve living standards in refugee camps and ease the sufferings of displaced and impoverished communities. Solar panels, biogas system, biomass stoves and micro wind turbines are some of the renewable energy systems that can be customized for refugee camps and transform them into a less harsh place for displaced people.

Tips to Choose the Budget-Friendly System of Energy

Newly arrived at your new home, the first thing is to make sure that you are going to pay the bill for the area that is in your use. That’s why the first day in your new home is advisable to take the meter reading. Good time to introduce yourself to the president of the community … or whoever wants to keep the keys of the accounting room. This advice also applies to gas, water, and other supplies whether it’s new construction or used housing, you should take a meter reading.  Look for iselect energy website! When moving, the first thing is to take note of the different counters (light, water, gas) in order to take responsibility only for what you are going to consume.

When moving, the first thing is to take note of the different counters (light, water, gas) in order to take responsibility only for what you are going to consume.

Your freedom of choice is sacred

It is very important that you know that you are always entitled to choose your electric company freely. You decide you send.  You have bought a house, or you are renting, this is a right of every consumer to choose the budget-friendly ways for electricity consumption. It is so legitimate that you are interested in changing or continuing with the electric company that you are hired.

What can you choose?

 The company that will send your electricity bill, that is, the electric energy trader.

What can you not choose?

The company that is responsible for providing the energy to your home, that is, the distributor. You do not choose it because you have to choose the one that corresponds to your place of residence.

When you arrive at a new house, it may happen that:

  1. The light is discharged, and both the power and the rate seem appropriate:

If so, and if you want to continue being a client of the same marketer, all you have to do is change the owner of the contract. This procedure is simple, fast and free.

  1. The light is discharged, but the power seems excessive or insufficient

You will have to make a change of power. This procedure costs money, although lowering the power can save a lot on your bill.

  1. The electricity connection is registered, but you want to change the tariff

When you arrive, you can “inherit” a contract with a certain company and a certain rate. If what you find does not convince you, you are free to change your electric energy provider. It is your choice, which service you want to choose for your home.

  1. The light has no connection to the electricity network

If your supply point has not been used for more than 3 years, this procedure costs money. The contract of registration is processed with the distributor, but it is the distributor that installs the meter and activates the supply. For this reason, the payment of this procedure will be made to the distributor in the first invoice.

The payment procedure for the efficient electricity providers is very simple and easy for the consumers. You can pay your bills and others online via credit and debit card.

MSW to Energy at a Glance

MSW-to-Energy is the use of thermochemical and biochemical technologies to recover energy, usually in the form of electricity and steam, from urban wastes. These new technologies can reduce the volume of the original waste by 90%, depending upon composition and use of outputs. The main categories of MSW-to-energy technologies are physical technologies, which process waste to make it more useful as fuel; thermal technologies, which can yield heat, fuel oil, or syngas from both organic and inorganic wastes; and biological technologies, in which bacterial fermentation is used to digest organic wastes to yield fuel.

Components of MSW-to-Energy Systems

  1. Front-end MSW preprocessing
  2. Conversion unit (reactor or anaerobic digester)
  3. Gas cleanup and residue treatment plant
  4. Energy recovery plant (optional)
  5. Emissions clean up

Incineration

  • Combustion of raw MSW, moisture less than 50%
  • Sufficient amount of oxygen is required to fully oxidize the fuel
  • Combustion temperatures are in excess of 850oC
  • Waste is converted into CO2 and water concern about toxics (dioxin, furans)
  • Any non-combustible materials (inorganic such as metals, glass) remain as a solid, known as bottom ash (used as feedstock in cement and brick manufacturing)
  • Fly ash APC (air pollution control residue) particulates, etc
  • Needs high calorific value waste to keep combustion process going, otherwise requires high energy for maintaining high temperatures

Anaerobic Digestion

  •  Well-known biochemical technology for organic fraction of MSW and domestic sewage.
  • Biological conversion of biodegradable organic materials in the absence of oxygen at mesophilic or thermophilic temperatures.
  • Residue is stabilized organic matter that can be used as soil amendment
  • Digestion is used primarily to reduce quantity of sludge for disposal / reuse
  • Methane gas is generated which is used for heat and power generation.

Gasification

  • Can be seen as between pyrolysis and combustion (incineration) as it involves partial oxidation.
  • Exothermic process (some heat is required to initialize and sustain the gasification process).
  • Oxygen is added but at low amounts not sufficient for full oxidation and full combustion.
  • Temperatures are above 650oC
  • Main product is syngas, typically has net calorific value of 4 to 10 MJ/Nm3
  • Other product is solid residue of non-combustible materials (ash) which contains low level of carbon

Pyrolysis

  • Thermal degradation of organic materials through use of indirect, external source of heat
  • Temperatures between 300 to 850oC are maintained for several seconds in the absence of oxygen.
  • Product is char, oil and syngas composed primarily of O2, CO, CO2, CH4 and complex hydrocarbons.
  • Syngas can be utilized for energy production or proportions can be condensed to produce oils and waxes
  • Syngas typically has net calorific value (NCV) of 10 to 20 MJ/Nm

Plasma Gasification

  • Use of electricity passed through graphite or carbon electrodes, with steam and/or oxygen / air injection to produce electrically conducting gas (plasma)
  • Temperatures are above 3000oC
  • Organic materials are converted to syngas composed of H2, CO
  • Inorganic materials are converted to solid slag
  • Syngas can be utilized for energy production or proportions can be condensed to produce oils and waxes
  •  

MSW-to-energy technologies can address a host of environmental issues, such as land use and pollution from landfills, and increasing reliance on fossil fuels. In many countries, the availability of landfill capacity has been steadily decreasing due to regulatory, planning and environmental permitting constraints. As a result, new approaches to waste management are rapidly being written into public and institutional policies at local, regional and national levels.

Biomass Cogeneration Systems

Biomass fuels are typically used most efficiently and beneficially when generating both power and heat through biomass cogeneration systems (also known as combined heat and power or CHP system). Biomass conversion technologies transform a variety of wastes into heat, electricity and biofuels by employing a host of strategies. Conversion routes are generally thermochemical or biochemical, but may also include chemical and physical.

The simplest way is to burn the biomass in a furnace, exploiting the heat generated to produce steam in a boiler, which is then used to drive a steam turbine. Advanced biomass conversion technologies include biomass integrated gasification combined cycle (BIGCC) systems, cofiring (with coal or gas), pyrolysis and second generation biofuels.

Biomass Cogeneration Systems

A typical biomass cogeneration (or biomass cogen) system provides:

  • Distributed generation of electrical and/or mechanical power.
  • Waste-heat recovery for heating, cooling, or process applications.
  • Seamless system integration for a variety of technologies, thermal applications, and fuel types into existing building infrastructure.

Biomass cogeneration systems consist of a number of individual components—prime mover (heat engine), generator, heat recovery, and electrical interconnection—configured into an integrated whole. The type of equipment that drives the overall system (i.e., the prime mover) typically identifies the CHP unit.

Prime Movers

Prime movers for biomass cogeneration units include reciprocating engines, combustion or gas turbines, steam turbines, microturbines, and fuel cells. These prime movers are capable of burning a variety of fuels, including natural gas, coal, oil, and alternative fuels to produce shaft power or mechanical energy.

Key Components

A biomass-fueled cogeneration facility is an integrated power system comprised of three major components:

  • Biomass receiving and feedstock preparation.
  • Energy conversion – Conversion of the biomass into steam for direct combustion systems or into biogas for the gasification systems.
  • Power and heat production – Conversion of the steam or syngas or biogas into electric power and process steam or hot water

Feedstock for Biomass Cogeneration Plants

The lowest cost forms of biomass for cogeneration plants are residues. Residues are the organic byproducts of food, fiber, and forest production, such as sawdust, rice husks, wheat straw, corn stalks, and sugarcane bagasse. Forest residues and wood wastes represent a large potential resource for energy production and include forest residues, forest thinnings, and primary mill residues.

combined-heat-and-power

Energy crops are perennial grasses and trees grown through traditional agricultural practices that are produced primarily to be used as feedstocks for energy generation, e.g. hybrid poplars, hybrid willows, and switchgrass. Animal manure can be digested anaerobically to produce biogas in large agricultural farms and dairies.

To turn a biomass resource into productive heat and/or electricity requires a number of steps and considerations, most notably evaluating the availability of suitable biomass resources; determining the economics of collection, storage, and transportation; and evaluating available technology options for converting biomass into useful heat or electricity.

Biomethane Utilization Pathways

biomethane-transportBiogas can be used in raw (without removal of CO2) or in upgraded form. The main function of upgrading biogas is the removal of CO2 (to increase the energy content) and H2S (to reduce risk of corrosion). After upgrading, biogas possesses identical gas quality properties as  natural gas, and can thus be used as natural gas replacement. The main pathways for biomethane utilization are as follows:

  • Production of heat and/or steam
  • Electricity production / combined heat and power production (CHP)
  • Natural gas replacement (gas grid injection)
  • Compressed natural gas (CNG) & diesel replacement – (bio-CNG for transport fuel usage)
  • Liquid natural gas (LNG) replacement – (bio-LNG for transport fuel usage)

Prior to practically all utilization options, the biogas has to be dried (usually through application of a cooling/condensation step). Furthermore, elements such as hydrogen sulphide and other harmful trace elements must be removed (usually trough application of an activated carbon filter) to prevent adverse effects on downstream processing equipment (such as compressors, piping, boilers and CHP systems).

Although biogas is perfectly suitable to be utilized in boilers (as an environmental friendlier source for heat and steam production), this option is rather obsolete due to the abundance of alternative sources from solid waste origin.

Most Palm Oil Mills are already self-reliant with respect to heat and steam production due to the combustion of their solid waste streams (such as EFB and PKS). Consequently, conversion to electricity (by means of a CHP unit) or utilization as natural gas, CNG or LNG replacement, would be a more sensible solution.

The biogas masterplan as drafted by the Asia Pacific Biogas Alliance foresees a distribution in which 30% of the biomethane is used for power generation, 40% for grid injection and 30% as compressed/liquefied fuel for transportation purpose (Asian Pacific Biogas Alliance, 2015).

For each project, the most optimal option has to be evaluated on a case to case basis. Main decision-making factors will be local energy prices and requirements, available infrastructure (for gas and electricity), incentives and funding.

For the locations where local demand is exceeded, and no electricity or gas infrastructure is available within a reasonable distance (<5-10 km, due to investment cost and power loss), production of CNG could offer a good solution.

Moreover, during the utilization of biogas within a CHP unit only 40-50% of the energetic content of the gas is converted into electricity. The rest of the energy is transformed into heat. For those locations where an abundance of heat is available, such as Palm Oil Mills, this effectively means that 50-60% of the energetic content of the biogas is not utilized. Converting the biogas into biomethane (of gas grid or CNG quality) through upgrading, would facilitate the transportation and commercialisation of over 95%  of the energetic content of the biogas.

Within the CNG utilization route, the raw biogas will be upgraded to a methane content of >96%, compressed to 250 bar and stored in racks with gas bottles. The buffered gas (bottles) will be suitable for transportation by truck or ship. For transportation over large distances (>200km), it will be advised to further reduce the gas volume by converting the gas to LNG (trough liquefaction).

Overall the effects and benefits from anaerobic digestion of POME and utilization of biomethane can be summarized as follows:

  • Reduction of emissions i.e. GHG methane and CO2
  • Reduced land use for POME treatment
  • Enhanced self-sufficiency trough availability of on-site diesel replacement (CNG)
  • Expansion of economic activities/generation of additional revenues
    • Sales of surplus electricity (local or to the grid)
    • Sales of biomethane (injection into the natural gas grid)
    • Replacement of on-site diesel usage by CNG
    • Sales of bottled CNG
  • Reducing global and local environmental impact (through fuel replacement)
  • Reducing dependence on fossil fuel, and enhances fuel diversity and security of energy supply
  • Enhancement of local infrastructure and employment
    • Through electrical and gas supply
    • Through Fuel (CNG) supply

Co-Authors: H. Dekker and E.H.M. Dirkse (DMT Environmental Technology)

Note: This is the second article in the special series on ‘Sustainable Utilization of POME-based Biomethane’ by Langerak et al of DMT Environmental Technology (Holland). The first article can be viewed at this link