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 Conveyors: An Overview

Biomass_ConveyorA well designed biomass conveyor system should take into account the variability of the material and provide the consistent and reliable flow that is crucial to power generation. Depending upon the type of boiler and conversion system, the fuel is either transported directly to the powerhouse via a belt conveyor, or first processed in a chipper/grinder to produce a finer texture. For example, municipal solid waste is deposited into pits where cranes mix the refuse and remove any large, non-combustible items. Sometimes, it is further processed to remove ferrous materials, glass, and other non-combustible materials.

For large pellet-fired biomass system, rail dump method is very common where railway tracks are constructed to transport biomass. Station is specified for train and fuel receiving bins are typically located below the track and rail cars dump into bins, either directly or through a rotary dumper. Fuel received is then transferred by belt conveyors to the biomass storage bins. For small particle size, pneumatic conveying system offer greater flexibility in routing than traditional belt conveyors. Equipment specific to pneumatic systems include positive displacement blowers and rotary feeders that function as air locks.

In a typical biomass thermal power plant, the initial process in the power generation is biomass fuel handling. A railway siding line is taken into the power station and the biomass is delivered in the storage yard. It is then unloaded from the point of delivery by means of wagon tippler. It is rack and pinion type. The biomass is taken from the unloading site to dead storage by belt conveyors. The belt deliver the biomass to warehouse.

The transfer points inside the warehouse are used to transfer biomass to the next belt. The belt elevates the biomass to breaker house. It consists of a rotary machine, which rotates the biomass and separates the light inorganic materials (viz. plastic or other incombustible particles) from it through the action of gravity and transfer it to reject bin house through belt. The belt further elevates the biomass until it reaches the crusher through belt. In the crusher a high-speed 3-phase induction motor is used to crush the biomass according to the requirement, for gasification size range is usually upto 15-20mm, while for biomass-fired boiler, size of 50mm is acceptable. Biomass rises from crusher house and reaches the dead storage.

Cost-effective production of biomass energy is very much dependent on efficient handling of available biomass sources, as well as the efficiency of each process. An important, but often overlooked, area is the efficient receiving of different types and different capacities of biomass as it enters the plant and then conveying this material to the production equipment.  In many cases, the space available for biomass handling is limited.

Receiving equipment can be installed in a pit or at the ground level. The size and volume of the receiving pocket can be suited to vehicle volumes or turn-around times. The receiving pit can be used as small buffer biomass storage or as an emergency or mixing pocket.

Belt conveyors are an economical and reliable choice for transferring biomass over long distances at high capacities with lower noise levels. Designs range from simple, open configurations to totally closed and washable conveyor galleries. Well engineered conveyors have the maximum safe distance between support legs to minimize the cost of civil construction as well as reducing the number of obstructions on the ground.

Chain conveyors are a reliable choice for transporting unscreened or dusty biomass, or when the available space is limited. Screw conveyors are a very economical alternative for transporting biomass over short distances.

Biomass conveyors are an integral feature of all biomass conversion routes

Nowadays, automated conveyor systems are getting traction around the world. Fully automated fuel handling systems employ a biomass storage bin that can hold upto 50 tons (or more) of biomass. The bin is filled by a self-unloading truck with negligible or no onsite staff assistance. From the biomass storage bunker, the fuel is fed automatically to the boiler by augers and conveyors. The fully automated system is a good match for biomass plants where maintenance staff has a large work load and cannot spend much time working with the biomass conversion plant.

Pellet-based hopper systems offer low costs for both installation and operation. In a modern biomass pellet boiler system, fuel is stored in a relatively low-cost grain silo and automatically fed, with no operator intervention, to the boiler or boilers with auger systems similar to those used for conveying feed grain on farms.

The fuel-handling system uses electric motors and is run by automated controls that provide the right amount of fuel to the combustion chamber based on facility demand. Such conveyor systems require minimal maintenance, around 20-30 minutes daily, for ash removal and maintenance of motors and augers, estimated to be about 20-30 minutes per day.

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.

Trends in Utilization of Palm Kernel Shells

palm-kernel-shell-usesThe palm kernel shells used to be initially dumped in the open thereby impacting the environment negatively without any economic benefit. However, over time, palm oil mills in Southeast Asia and elsewhere realized their brilliant properties as a fuel and that they can easily replace coal as an industrial fuel for generating heat and steam.

Major Applications

Nowadays, the primary use of palm kernel shells (PKS) is as a boiler fuel supplementing the fibre which is used as primary fuel. In recent years kernel shells are extensively sold as alternative fuel around the world. Besides selling shells in bulk, there are companies that produce fuel briquettes from shells which may include partial carbonisation of the material to improve the combustion characteristics.

Palm kernel shells have a high dry matter content (>80% dry matter). Therefore the shells are generally considered a good fuel for the boilers as it generates low ash amounts and the low K and Cl content will lead to less ash agglomeration. These properties are also ideal for production of biomass for export.

As a raw material for fuel briquettes, palm shells are reported to have the same calorific characteristics as coconut shells. The relatively smaller size makes it easier to carbonise for mass production, and its resulting palm shell charcoal can be pressed into a heat efficient biomass briquette.

Although the literature on using oil palm shells (and fibres) is not as extensive as EFB, common research directions of using shells, besides energy, are to use it as raw material for light-weight concrete, fillers, activated carbon, and other materials. However, none of the applications are currently done on a large-scale. Since shells are dry and suitable for thermal conversion, technologies that further improve the combustion characteristics and increase the energy density, such as torrefaction, could be relevant for oil palm shells.

Torrefaction is a pretreatment process which serves to improve the properties of biomass in relation to the thermochemical conversion technologies for more efficient energy generation. High lignin content for shells affects torrefaction characteristics positively (as the material is not easily degraded compared to EFB and fibres).

Furthermore, palm oil shells are studied as feedstock for fast pyrolysis. To what extent shells are a source of fermentable sugars is still not known, however the high lignin content in palm kernel shells indicates that shells are less suitable as raw material for fermentation.

Future Outlook

The leading palm oil producers in the world should consider limiting the export of palm-kernel shells (PKS) to ensure supplies of the biomass material for renewable energy projects, in order to decrease dependency on fossil fuels. For example, many developers in Indonesia have expressed an interest in building palm kernel shell-fired power plants. However, they have their concerns over supplies, as many producers prefer to sell their shells overseas currently. Many existing plants are facing problems on account of inconsistent fuel quality and increasing competition from overseas PKS buyers. PKS market is well-established in provinces like Sumatra and export volumes to Europe and North Asia as a primary fuel for biomass power plants is steadily increasing.

The creation of a biomass supply chain in palm oil producing countries may be instrumental in discouraging palm mills to sell their PKS stocks to brokers for export to foreign countries. Establishment of a biomass exchange in leading countries, like Indonesia, Malaysia and Nigeria, will also be a deciding factor in tapping the unharnessed potential of palm kernel shells as biomass resource.