Global Trends in the Biomass Sector

There has been a flurry of activity in the biomass energy and waste-to-energy sector in recent year, with many new projects and initiatives being given the green light across the globe. This movement has been on both a regional and local level; thanks to the increased efficiency of green energy generators and a slight lowering in implementation costs, more businesses and even some homeowners are converting waste-to-energy systems or by installing biomass energy units.

Latest from the United Kingdom

Our first notable example of this comes from Cornwall in the UK. As of this week, a small hotel has entirely replaced its previous oil-based heating system with biomass boilers. Fuelled from wood wastes brought in from a neighboring forest, the BudockVean hotel has so far been successful in keeping the entire establishment warm on two small boilers despite it being the height of British winter – and when warmer weather arrives, plans to install solar panels on the building’s roof is to follow.

Similar projects have been undertaken across small businesses in Britain, including the south-coast city of Plymouth that has just been announced to house a 10MW biomass power plant (alongside a 20MW plant already in construction). These developments arein part thanks to the UK government’s Renewable Heat Incentive which was launched back in 2011. The scheme only provides funding to non-domestic properties currently, but a domestic scheme is in the works this year to help homeowners also move away from fossil fuels.

Initiatives (and Setbacks) in the US

Back across the pond, and the state of New York is also launching a similar scheme. The short-term plan is to increase public education on low-emission heating and persuade a number of large business to make the switch; in the longer term, $800m will be used to install advanced biomass systems in large, state-owned buildings.

A further $40m will be used as part of a competition to help create a series of standalone energy grids in small towns and rural areas, which is a scheme that could hopefully see adopted beyond New York if all goes well.


Unfortunately, the move away from fossil fuels hasn’t been totally plain sailing across the US. Georgia suffered a blow this week as plans to convert a 155MW coal plant to biomass have been abandoned, citing large overheads and low projected returns. The company behind the project have met similar difficulties at other sites, but as of this week are moving ahead with further plans to convert over 2000MW of oil and coal energy generation in the coming years.

Elsewhere in the US, a company has conducted a similar study as to whether biomass plant building will be feasible in both Florida and Louisiana. Surveying has only just been completed, but if things go better than the recent developments in Georgia, the plants will go a long way to converting biomass to fertilizer for widespread use in agriculture in both states.

Far East Leading the Way

One country that is performing particularly well in biomass energy investment market is Japan. Biomass is being increasingly used in power plants in Japan as a source of fuel, particularly after the tragic accident at Fukushima nuclear power plant in 2011.  Palm kernel shell (PKS) has emerged as a favorite choice of biomass-based power plants in the country. Most of these biomass power plants use PKS as their energy source, and only a few operate with wood pellets. Interestingly, most of the biomass power plants in Japan have been built after 2015..

On the contrary, the US and Europe saw a fairly big fall in financing during this period; it should be noted, however, that this relates to the green energy investment market as a whole as opposed to biomass-specific funding. The increase seen in Japan has been attributed to an uptake in solar paneling, and if we look specifically to things such as the global demand for biomass pellets, we see that the most recent figures paint the overall market in a much more favorable light for the rest of the world.

Brighter Times Ahead

All in all, it’s an exciting time for the biomass industry despite the set backs which are being experienced in some regions.  On the whole, legislators and businesses are working remarkably well together in order to pave the way forward – being a fairly new market (from a commercially viable sense at least), it has taken a little while to get the ball rolling, but expect to see it blossom quickly now that the idea of biomass is starting to take hold.

Biomass Pelletization Process

Biomass pellets are a popular type of biomass fuel, generally made from wood wastes, agricultural biomass, commercial grasses and forestry residues. In addition to savings in transportation and storage, pelletization of biomass facilitates easy and cost effective handling. Dense cubes pellets have the flowability characteristics similar to those of cereal grains. The regular geometry and small size of biomass pellets allow automatic feeding with very fine calibration. High density of pellets also permits compact storage and rational transport over long distance. Pellets are extremely dense and can be produced with a low moisture content that allows them to be burned with very high combustion efficiency.

Biomass pelletization is a standard method for the production of high density, solid energy carriers from biomass. Pellets are manufactured in several types and grades as fuels for electric power plants, homes, and other applications. Pellet-making equipment is available at a variety of sizes and scales, which allows manufacture at domestic as well industrial-scale production. Pellets have a cylindrical shape and are about 6-25 mm in diameter and 3-50 mm in length. There are European standards for biomass pellets and raw material classification (EN 14961-1, EN 14961-2 and EN 14961-6) and international ISO standards under development (ISO/DIS 17225-1, ISO/DIS 17225-2 and ISO/DIS 17225-6).

Process Description

The biomass pelletization process consists of multiple steps including raw material pre-treatment, pelletization and post-treatment. The first step in the pelletization process is the preparation of feedstock which includes selecting a feedstock suitable for this process, its filtration, storage and protection. Raw materials used are sawdust, wood shavings, wood wastes, agricultural residues like straw, switchgrass etc. Filtration is done to remove unwanted materials like stone, metal, etc. The feedstock should be stored in such a manner that it is away from impurities and moisture. In cases where there are different types of feedstock, a blending process is used to achieve consistency.

The moisture content in biomass can be considerably high and are usually up to 50% – 60% which should be reduced to 10 to 15%. Rotary drum dryer is the most common equipment used for this purpose. Superheated steam dryers, flash dryers, spouted bed dryers and belt dryers can also be used. Drying increases the efficiency of biomass and it produces almost no smoke on combustion. It should be noted that the feedstock should not be over dried, as a small amount of moisture helps in binding the biomass particles. The drying process is the most energy intensive process and accounts for about 70% of the total energy used in the pelletization process.

Schematic of Pelletization of Woody Biomass

Before feeding biomass to pellet mills, the biomass should be reduced to small particles of the order of not more than 3mm.  If the pellet size is too large or too small, it affects the quality of pellet and in turn increases the energy consumption. Therefore the particles should have proper size and should be consistent. Size reduction is done by grinding using a hammer mill equipped with a screen of size 3.2 to 6.4 mm. If the feedstock is quite large, it goes through a chipper before grinding.

The next and the most important step is pelletization where biomass is compressed against a heated metal plate (known as die) using a roller. The die consists of holes of fixed diameter through which the biomass passes under high pressure. Due to the high pressure, frictional forces increase, leading to a considerable rise in temperature. High temperature causes the lignin and resins present in biomass to soften which acts as a binding agent between the biomass fibers. This way the biomass particles fuse to form pellets.

The rate of production and electrical energy used in the pelletization of biomass  are strongly correlated to the raw material type and processing conditions such as moisture content and feed size. The The average energy required to pelletize biomass is roughly between 16 kWh/t and 49kWh/t. During pelletization, a large fraction of the process energy is used to make the biomass flow into the inlets of the press channels.

Binders or lubricants may be added in some cases to produce higher quality pellets. Binders increase the pellet density and durability. Wood contains natural resins which act as a binder. Similarly, sawdust contains lignin which holds the pellet together. However, agricultural residues do not contain much resins or lignin, and so a stabilizing agent needs to be added in this case. Distillers dry grains or potato starch is some commonly used binders. The use of natural additives depends on biomass composition and the mass proportion between cellulose, hemicelluloses, lignin and inorganics.

Due to the friction generated in the die, excess heat is developed. Thus, the pellets are very soft and hot (about 70 to 90oC). It needs to be cooled and dried before its storage or packaging. The pellets may then be passed through a vibrating screen to remove fine materials. This ensures that the fuel source is clean and dust free.

The pellets are packed into bags using an overhead hopper and a conveyor belt. Pellets are stored in elevated storage bins or ground level silos. The packaging should be such that the pellets are protected from moisture and pollutants. Commercial pellet mills and other pelletizing equipment are widely available across the globe.

Biomass Energy in China

biomass-chinaBiomass energy in China has been developing at a rapid pace. The installed biomass power generation capacity in China increased sharply from 1.4 GW in 2006 to 14.88 GW in 2017. While the energy share of biomass remains relatively low compared to other sources of renewable energy, China plans to increase the proportion of biomass energy up to 15 percent and total installed capacity of biomass power generation to 30 GW by 2030.

In terms of impact, the theoretical biomass energy resource in China is about 5 billion tons coal equivalent, which equals 4 times of all energy consumption. As per conservative estimates, currently China is only using 5 percent of its total biomass potential.

According to IRENA, the majority of biomass capacity is in Eastern China, with the coastal province of Shandong accounting for 14 percent of the total alone. While the direct burning of mass for heat remains the primary use of biomass in China, in 2009, composition of China’s biomass power generation consisted in 62 percent of straw direct-fired power generation and 29 percent of waste incineration, with a mix of other feedstock accounting for the remaining 9 percent.

Biomass Resources in China

Major biomass resources in China include waste from agriculture, forestry, industries, animal manure and sewage, and municipal solid waste. While the largest contributing sources are estimated to be residues from annual crop production like wheat straw, much of the straw and stalk are presently used for cooking and heating in rural households at low efficiencies. Therefore, agricultural residues, forestry residues, and garden waste were found to be the most cited resources with big potential for energy production in China.

Agricultural residues are derived from agriculture harvesting such as maize, rice and cotton stalks, wheat straw and husks, and are most available in Central and northeastern China where most of the large stalk and straw potential is located. Because straw and stalks are produced as by-products of food production systems, they are perceived to be sustainable sources of biomass for energy that do not threaten food security.

Furthermore, it is estimated that China produces around 700 Mt of straw per year, 37 percent of which is corn straw, 28 percent rice, 20 percent wheat and 15 percent from various other crops. Around 50 percent of this straw is used for fertilizers, for which 350 Mt of straw is available for energy production per year.

Biomass resources are underutilized across China

Biomass resources are underutilized across China

Forestry residues are mostly available in the southern and central parts of China. While a few projects that use forestry wastes like tree bark and wood processing wastes are under way, one of the most cited resources with analyzed potential is garden waste. According to research, energy production from garden waste biomass accounted for 20.7 percent of China’s urban residential electricity consumption, or 12.6 percent of China’s transport gasoline demand in 2008.

Future Perspectives

The Chinese government believes that biomass feedstock should neither compete with edible food crops nor cause carbon debt or negative environmental impacts. As biomass takes on an increasing significant role in the China’s national energy-mix, future research specific to technology assessment, in addition to data collection and supply chain management of potential resources is necessary to continue to understand how biomass can become a game-changer in China’s energy future.

References

IRENA, 2014. Renewable Energy Prospects: China, REmap 2030 analysis. IRENA, Abu Dhabi. www.irena.org/remap

National Academy of Engineering and NRC, 2007: Energy Futures and Urban Air Pollution: Challenges for China and the United States.

Xingang, Z., Zhongfu, T., Pingkuo, L, 2013. Development goal of 30 GW for China’s biomass power generation: Will it be achieved? Renewable and Sustainable Energy Reviews, Volume 25, September 2013, 310–317.

Xingang, Z., Jieyu, W., Xiaomeng, L., Tiantian, F., Pingkuo, L, 2012. Focus on situation and policies for biomass power generation in China. Renewable and Sustainable Energy Reviews, Volume 16, Issue 6, August 2012, 3722–3729.

Li, J., Jinming, B. MOA/DOE Project Expert Team, 1998. Assessment of Biomass Resource Availability in China. China Environmental Science Press, Beijing, China.

Klimowicz, G., 2014. “China’s big plans for biomass,” Eco-Business, Global Biomass Series, accessed on Apr 6, 2015.

Shi, Y., Ge, Y., Chang, J., Shao, H., and Tang, Y., 2013. Garden waste biomass for renewable and sustainable energy production in China: Potential, challenges and development. Renewable and Sustainable Energy Reviews 22 (2013) 432–437

Xu, J. and Yuan, Z, 2015. “An overview of the biomass energy policy in China,” BESustainable, May 21, 2015.

A Glance at Woody Biomass Resources

Woody biomass resources range from corn kernels to corn stalks, from soybean and canola oils to animal fats, from prairie grasses to hardwoods, and even include algae. Woody biomass may be used for energy production at different scales, including large-scale power generation, CHP, or small-scale thermal heating projects. Some of the major sources of woody biomass are being discussed in the following paragraphs:

Pulp and Paper Industry Residues

The largest source of energy from wood is the waste product from the pulp and paper industry called black liquor. Logging and processing operations generate vast amounts of biomass residues. Wood processing produces sawdust and a collection of bark, branches and leaves/needles. A paper mill, which consumes vast amount of electricity, utilizes the pulp residues to create energy for in-house usage.

Forest Residues

Forest harvesting is a major source of biomass for energy. Harvesting may occur as thinning in young stands, or cutting in older stands for timber or pulp that also yields tops and branches usable for bioenergy. Harvesting operations usually remove only 25 to 50 percent of the volume, leaving the residues available as biomass for energy. Stands damaged by insects, disease or fire are additional sources of biomass. Forest residues normally have low density and fuel values that keep transport costs high, and so it is economical to reduce the biomass density in the forest itself.

Agricultural or Crop Residues

Crop residues encompasses all agricultural wastes such as straw, stem, stalk, leaves, husk, shell, peel, pulp, stubble, etc. which come from cereals (rice, wheat, maize or corn, sorghum, barley, millet), cotton, groundnut, jute, legumes (tomato, bean, soy) coffee, cacao, tea, fruits (banana, mango, coco, cashew) and palm oil.

Rice produces both straw and rice husks at the processing plant which can be conveniently and easily converted into energy. Significant quantities of biomass remain in the fields in the form of cob when maize is harvested which can be converted into energy. Sugar cane harvesting leads to harvest residues in the fields while processing produces fibrous bagasse, both of which are good sources of energy.

Energy Crops

Dedicated energy crops are another source of woody biomass for energy. These crops are fast-growing plants, trees or other herbaceous biomass which are harvested specifically for energy production. Rapidly-growing, pest-tolerant, site and soil-specific crops have been identified by making use of bioengineering. For example, operational yield in the northern hemisphere is 10-15 tonnes/ha annually. A typical 20 MW steam cycle power station using energy crops would require a land area of around 8,000 ha to supply energy on rotation.

Herbaceous energy crops are harvested annually after taking two to three years to reach full productivity. These include grasses such as switchgrass, elephant grass, bamboo, sweet sorghum, wheatgrass etc. Short rotation woody crops are fast growing hardwood trees harvested within five to eight years after planting. These include poplar, willow, silver maple, cottonwood, green ash, black walnut, sweetgum, and sycamore.

Industrial crops are grown to produce specific industrial chemicals or materials, e.g. kenaf and straws for fiber, and castor for ricinoleic acid. Agricultural crops include cornstarch and corn oil soybean oil and meal wheat starch, other vegetable oils etc. Aquatic resources such as algae, giant kelp, seaweed, and microflora also contribute to bioenergy feedstock.

Urban Wood Wastes

Such waste consists of lawn and tree trimmings, whole tree trunks, wood pallets and any other construction and demolition wastes made from lumber. The rejected woody material can be collected after a construction or demolition project and turned into mulch, compost or used to fuel bioenergy plants.

Biomass from Wood Processing Industries

Wood processing industries primarily include sawmilling, plywood, wood panel, furniture, building component, flooring, particle board, moulding, jointing and craft industries. Biomass from wood processing industries is generally concentrated at the processing factories, e.g. plywood mills and sawmills. The amount of waste generated from wood processing industries varies from one type industry to another depending on the form of raw material and finished product.

Biomass from Wood Processing

The waste resulted from a wood processing is influenced by the diameter of logs being processed, type of saw, specification of product required and skill of workers. Generally, the waste from wood industries such as saw millings and plywood, veneer and others are sawdust, off-cuts, trims and shavings.

Sawdust arise from cutting, sizing, re-sawing, edging, while trims and shaving are the consequence of trimming and smoothing of wood. In general, processing of 1,000 kilos of wood in the furniture industries will lead to wood waste generation of almost half (45 %), i.e. 450 kilos of wood. Similarly, when processing 1,000 kilos of wood in sawmill, the waste will amount to more than half (52 %), i.e. 520 kilo of wood.

The biomass wastes generated from wood processing industries include sawdust, off-cuts and bark. Recycling of wood wastes is not done by all wood industries, particularly small to medium scale wood industries. The off-cuts and cutting are sold or being used as fuel for wood drying process. Bark and sawdust are usually burned.

Recycling of Wood Wastes

The use of wood wastes is usually practised in large and modern establishment; however, it is commonly only used to generate steam for process drying. The mechanical energy demand such as for cutting, sawing, shaving and pressing is mostly provided by diesel generating set and/or electricity grid. The electricity demand for such an industry is substantially high.

Recycling of wood wastes is not done by all wood industries, particularly by smallholders. These wastes are normally used as fuel for brick making and partly also for cooking. At medium or large establishments some of the wastes, like: dry sawdust and chips, are being used as fuel for wood drying process. Bark and waste sawdust are simply burned or dumped.

Importance of Heating Value

The heating or calorific value is a key factor when evaluating the applicability of a combustible material as a fuel. The heating value of wood and wood waste depends on the species, parts of the tree that are being used (core, bark, stem, wood, branch wood, etc.) and the moisture content of the wood. The upper limit of the heating or calorific value of 100% dry wood on a weight basis is relatively constant, around 20 MJ/kg.

In practice, the moisture content of wood during logging is about 50%. Depending on transportation and storing methods and conditions it may rise to 65% or fall to some 30% at the mill site. The moisture content of the wood waste in an industry depends on the stage where the waste is extracted and whether wood has been dried before this stage.

Biomass Resources in Malaysia

Malaysia is gifted with conventional energy resources such as oil and gas as well as renewables like hydro, biomass and solar energy. As far as biomass resources in Malaysia are concerned, Malaysia has tremendous agricultural biomass and wood waste resources available for immediate exploitation. This energy potential of biomass resource is yet to be exploited properly in the country.

Taking into account the growing energy consumption and domestic energy supply constraints, Malaysia has set sustainable development and diversification of energy sources, as the economy’s main energy policy goals. The Five-Fuel Strategy recognises renewable energy resources as the economy’s fifth fuel after oil, coal, natural gas and hydro. Being a major agricultural commodity producer in the region Malaysia is well positioned amongst the ASEAN countries to promote the use of biomass as a source of renewable energy.

Major Biomass Resources

Palm Oil Biomass

Malaysia is the world’s leading exporter of palm oil, exporting more than 19.9 million tonnes of palm oil in 2017. The extraction of palm oil from palm fruits results in a large quantity of waste in the form of palm kernel shells, empty fruit bunches and mesocarp fibres. In 2011, more than 80 million tons of oil palm biomass was generated across the country.

13MW biomass power plant at a palm oil mill in Sandakan, Sabah (Malaysia)

Processing crude palm oil generates a foul-smelling effluent, called Palm Oil Mill Effluent or POME, which when treated using anaerobic processes, releases biogas. Around 58 million tons of POME is produced in Malaysia annually, which has the potential to produce an estimated 15 billion m3 of biogas.

Rice Husk

Rice husk is another important agricultural biomass resource in Malaysia with very good energy potential for biomass cogeneration. An example of its attractive energy potential is biomass power plant in the state of Perlis which uses rice husk as the main source of fuel and generates 10 MW power to meet the requirements of 30,000 households.

Municipal Solid Wastes

The per capita generation of solid waste in Malaysia varies from 0.45 to 1.44kg/day depending on the economic status of an area. Malaysian solid wastes contain very high organic waste and consequently high moisture content and bulk density of above 200kg/m3. The high rate of population growth is the country has resulted in rapid increase in solid waste generation which is usually dumped in landfills.

Conclusion

Biomass resources have long been identified as sustainable source of renewable energy particularly in countries where there is abundant agricultural activities. Intensive use of biomass as renewable energy source in Malaysia could reduce dependency on fossil fuels and significant advantage lies in reduction of net carbon dioxide emissions to atmosphere leading to less greenhouse effect. However, increased competitiveness will require large-scale investment and advances in technologies for converting this biomass to energy efficiently and economically.

Bioenergy Perspectives for Southeast Asia

Southeast Asia, with its abundant bioenergy resources, holds a strategic position in the global biomass energy atlas. There is immense bioenergy potential in Southeast Asian countries due to plentiful supply of diverse forms of biomass wastes such as agricultural residues, woody biomass, animal wastes, municipal solid waste, etc. The rapid economic growth and industrialization in the region has accelerated the drive to implement the latest waste-to-energy technologies to tap the unharnessed potential of biomass resources.

Southeast Asia is a big producer of agricultural and wood products which, when processed in industries, produces large amounts of biomass residues. According to conservative estimates, the amount of biomass residues generated from sugar, rice and palm oil mills is more than 200-230 million tons per year which corresponds to cogeneration potential of 16-19 GW.

Rice mills in the region produce 38 million tonnes of rice husk as solid residue which is a good fuel for producing heat and power. Sugar industry is an integral part of the industrial scenario in Southeast Asia accounting for 7% of sugar production worldwide. Sugar mills in Thailand, Indonesia, Philippines and Vietnam generate 34 million tonnes of bagasse every year.  Malaysia, Indonesia and Thailand account for 90% of global palm oil production leading to the generation of 27 million tonnes of waste per annum in the form of empty fruit bunches (EFBs), fibers and shells, as well as liquid effluent.

Woody biomass is a good energy resource due to presence of large number of forests in Southeast Asia. Apart from natural forests, non-industrial plantations of different types (e.g. coconut, rubber and oil palm plantations, fruit orchards, and trees in homesteads and gardens) have gained recognition as important sources of biomass. In addition, the presence of a large number of wood processing industries also generates significant quantity of wood wastes. The annual production of wood wastes in the region is estimated to be more than 30 million m3.

The prospects of biogas power generation are also high in the region thanks to presence of well-established food-processing and dairy industries. Another important biomass resource is contributed by municipal solid wastes in heavily populated urban areas.  In addition, there are increasing efforts both commercially and promoted by governments to develop biomass energy systems for efficient biofuel production, e.g. bio-diesel from palm oil.

Biomass resources, particularly residues from forests, wood processing, agricultural crops and agro-processing, are under-utilised in Southeast Asian countries. There is an urgent need to utilize biomass wastes for commercial electricity and heat production to cater to the needs of the industries as well as urban and rural communities.

Southeast Asian countries are yet to make optimum use of the additional power generation potential from biomass waste resources which could help them to partially overcome the long-term problem of energy supply. Technologies for biomass utilization which are at present widely used in Southeast counties need to be improved towards best practice by making use of the latest trends in the biomass energy sector.