Wood Pellet Boiler Heats School for 3,000 Children
in Burgas

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The pellets hot water boiler was installed in the renovated and modernized plant in the Burgas complex, Meden Rudnik, in July 2019. The boiler will produce cleaner and cheaper heat energy for the Elin Pelin elementary school, the Konstantin Petkanov high school and the Morska Zvezda kindergarten. The energy is obtained through controlled burning of biomass in the form of wood pellets, and has a maximum heating output of 1650 kW, a built-in fuel hopper with a capacity of 1400 liters and a fire-fighting system. The new boiler replaced the old one which was inefficient, heavily corroded, and had numerous leaks and accidents.

The project is implemented by the municipality of Burgas, and includes a chimney and silo of 30 cubic meters built for the storage of the wooden pellets, a new circulating pumps room station installation and isolated pipes used for the new underground heat distribution network from the plant to the two schools and kindergarten which it supplies. Along the route, new pre-insulated pipelines consisting of steel tubes, insulated with polyurethane foam and a polyethylene tube sheath, were installed to the schools.

The financing of the project is provided by the BG04 Program “Energy Efficiency and Renewable Energy” under the Financial Mechanism of the European Economic Area 2009-2014. The partners of Burgas municipality are “Technical University – Sofia – Technologies” Ltd. and “NORSK ENERGI” – Norway. The contractor of the project is the company “Thermal Engineering” Ltd.

The delivery and installation of the biomass boiler manufactured by D’Alessandro Termomeccanica Srl, Italy and the installation of underground heat pipelines are part of the implementation of the project, “Increasing the energy efficiency of central district heating in three municipal buildings for education in Meden Rudnik complex”, which the municipality authority has won.

The reconstruction of the plant and the replacement of the connecting pipelines will guarantee much better heating for thousands of children, reducing financial costs. Last but not least – it will provide cleaner air for the residents of the complex, as it emitted many times more harmful emissions before the repair.

This project is the final touch in the campaign to improve energy efficiency in the schools of the huge residential complex. For several years the municipality of Burgas managed to renovate the buildings of absolutely all schools and kindergartens here.

Solid Biomass Conversion Processes

Logging, grinding, screening and drying operations are mechanical processes for enhancing solid biomass fuels. These operations help transform biomass into homogeneous fuel that is easy to handle, with a higher energy recovery (eg. woodchips, wood logs, agrofuel). In general, moisture content in woodchips used for energy generation in municipal or industrial plants ranges between 20-30%.

Densification is another popular way to transform woody material into an advanced fuel with high calorific value. This process involves compressing biomass and lowering moisture levels to a range of 8-10%, allowing for an homogenous fuel – either in the form of pellets or briquettes. The heat during compression fuses the lignin in the biomass, naturally binding the biomass together in a new, enhanced shape. Thanks to densification, the homogenous biomass fuel is easier to transport and can be used in automated biomass installations, such as pellet stoves and boilers.

Thermo-chemical conversions are now used to produce fuel with even higher calorific value, utilising torrefaction or steam explosion technologies. During the torrefaction process, wood is subjected to temperatures of 230°C-300°C at atmospheric pressure without oxygen. Comparable to some extent to coffee torrefaction, this method creates a fuel with unique characteristics. As compared to conventional wood, torrefied wood has very low (>5%) moisture content, is easily grindable and is relatively hydrophobic.

Thanks to advanced technologies, woody biomass can also produce liquid and gaseous fuels. Pyrolysis, for instance, is a thermal-chemical conversion that requires a high temperature (>400°C) and little oxygen to convert solid biomass into gas, liquid fuels (pyrolysis oil) and/or biochar. Gasification is another thermo-chemical conversion that takes place at high temperatures (>800°C), with limited oxygen and/or steam, and converts solid biomass into synthesis gas, known as syngas – which contains carbon and hydrogen and can be used to produce liquid fuels such as biodiesel.

Wet Biomass Conversion Processes

Wet biomass is present in high volume across Europe (manure, agricultural waste and by-products). As it contains too much moisture to be converted efficiently into energy via a direct combustion process, other conversion pathways and energy outputs have been developed by the biogas (eg. anaerobic digestion) and biofuel sectors (eg. fermentation). Anaerobic digestion and fermentation are the two main conversion pathways used for converting wet biomass feedstock into advanced fuel.

Anaerobic digestion is the microbiological process of decomposition of organic matter, in the absence of oxygen, and is common to many natural environments; it is largely applied today in order to produce biogas in airproof reactor tanks, commonly referred to as digesters. A wide range of micro-organisms are involved in the anaerobic process which has two main end products: biogas and digestate. Biogas is a combustible gas consisting of methane, carbon dioxide and small amounts of other gases and trace elements. Biogas can be used in direct combustion to produce heat, but also power if converted within a cogeneration plant or in adapted gas motors. Biogas can also be upgraded via purification processes to a biomethane that can be injected into the existing natural gas networks, used as a chemical product and/or vehicle fuel. Digestate is the decomposed substrate, rich in macro- and micro-nutrients and therefore suitable for use as plant fertiliser.

Fermentation is a biochemical conversion whereby microorganisms, including yeast and bacteria, convert matter into products such as ethanol and liquid transport fuel (biodiesel). This process is done in several stages. First, sugary and starchy feedstock such as corn must be crushed and combined with water, allowing enzymes to convert this starch into sugar. This ferments along with the addition of yeast and is distilled into bioethanol. Bioethanol can also be produced from cellulosic biomass, such as grass, wood and stalks, via fermentation; however, this process is more complex and involves a mechanical pre-treatment and the addition of enzymes, or the breakdown of the lignocellulose into sugar through hydrolysis, followed by the same procedure.

Solid bioenergy feedstock

Renewables represent 8,0% of EU-27 total energy consumption (22.473 kilotonnes of oil equivalent) in transportation, of which 68% is provided by biofuels in 2018. It is rather challenging to foresee how biofuels (in particular first-generation biofuels) will continue to develop, since recent EU legislation established a quota for these biofuels. EU statistics on renewables in transportation can also be misleading regarding the actual level of production, because multiple counting rules are applied in accordance with the EU renewable energy directive. Looking at it in more detail, the biofuel market is driven by biodiesel and bioethanol. Biodiesel was the first biofuel developed and used in the EU in the transport sector in the 1990s. EU-27 remains the world’s largest biodiesel producer and it consumed 13,303 Ktoe in 2018. By comparison, bioethanol consumption in 2018 reached 2,620 Ktoe for an actual production of 2,365 Ktoe (Biofuels Report, 2020).

Bioenergy comes in all shapes and sizes

Within our close environment, a great source of organic materials such as plants, algae, or organic wastes, can be valuable fuels as soon as a technology makes it possible to efficiently extract all of its energy potential. Bioenergy players traditionally refer to biomass to describe those usable feedstocks. Biomass currently used in Europe includes wood from forests, agricultural crops and residues, by-products from the wood and agricultural industry, herbaceous and woody energy crops, municipal organic wastes and manure, and could potentially integrate algae and marine biomass in the future.

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Wood Pellet Boiler Heats School for 3,000 Childrenin Burgas

Bioenergy comes in all shapes and sizes

Wood Pellet Boiler Heats School for 3,000 Children
in Burgas