Biomass heating systems generate heat from biomass. The systems may use direct combustion, gasification, combined heat and power (CHP), anaerobic digestion or aerobic digestion to produce heat. Biomass heating may be fully automated or semi-automated they may be pellet-fired, or they may be combined heat and power systems .
There are four main types of heating systems that use biomass to heat a boiler. The types of biomass heating are fully automated, semi-automated, pellet-fired, and combined heat and power.
In fully automated systems chipped or ground up biomass is fed to the boiler via conveyors at a managed rate. This rate is managed by computer controls to maintain the pressure and temperature within the boiler. Fully automated systems offer a great deal of ease in their operation because they only require the operator of the system to control the computer. [1] [2]
Semi-automated or "Surge Bin" systems are very similar to fully automated systems except they require more manpower to keep operational. They have smaller holding tanks, and a much simpler conveyor systems which will require personnel to maintain the systems operation. The reasoning for the changes from the fully automated system is the efficiency of the system. The heat created by the combustor can be used to directly heat the air or it can be used to heat water in a boiler system which acts as the medium by which the heat is delivered. [3] Wood fire fuelled boilers are most efficient when they are running at their highest capacity, and the heat required most days of the year will not be the peak heat requirement for the year. Considering that the system will only need to run at a high capacity a few days of the year, it is made to meet the requirements for the majority of the year to maintain its high efficiency. [2]
The third main type of biomass heating systems are pellet-fired systems. Pellets are a processed form of wood, which make them more expensive. Although they are more expensive, they are much more condensed and uniform, and therefore are more efficient. Further, it is relatively easy to automatically feed pellets to boilers. In these systems, the pellets are stored in a grain-type storage silo, and gravity is used to move them to the boiler. The storage requirements are much smaller for pellet-fired systems because of their condensed nature, which also helps cut down costs. these systems are used for a wide variety of facilities, but they are most efficient and cost effective for places where space for storage and conveyor systems is limited, and where the pellets are made fairly close to the facility. [2]
One subcategory of pellet systems are boilers or burners capable of burning pellet with higher ash rate (paper pellets, hay pellets, straw pellets). One of this kind is PETROJET pellet burner with rotating cylindrical burning chamber. [4] In terms of efficiencies advanced pellet boilers can exceed other forms of biomass because of the more stable fuel characteristics. Advanced pellet boilers can even work in condensing mode and cool down combustion gases to 30-40°C, instead of 120°C before sent into the flue. [5]
Combined heat and power systems are very useful systems in which wood waste, such as wood chips, is used to generate power, and heat is created as a byproduct of the power generation system. They have a very high cost because of the high pressure operation. Because of this high pressure operation, the need for a highly trained operator is mandatory, and will raise the cost of operation. Another drawback is that while they produce electricity they will produce heat, and if producing heat is not desirable for certain parts of the year, the addition of a cooling tower is necessary, and will also raise the cost.
There are certain situations where CHP is a good option. Wood product manufacturers would use a combined heat and power system because they have a large supply of waste wood, and a need for both heat and power. Other places where these systems would be optimal are hospitals and prisons, which need energy, and heat for hot water. These systems are sized so that they will produce enough heat to match the average heat load so that no additional heat is needed, and a cooling tower is not needed. [2]
The use of biomass in heating systems is beneficial because it uses agricultural, forest, urban and industrial residues and waste to produce heat and/or electricity with less effect on the environment than fossil fuels. [6] This type of energy production has a limited long-term effect on the environment because the carbon in biomass is part of the natural carbon cycle; while the carbon in fossil fuels is not, and permanently adds carbon to the environment when burned for fuel (carbon footprint). [7] Historically, before the use of fossil fuels in significant quantities, biomass in the form of wood fuel provided most of humanity's heating.
Because forest based biomass is typically derived from wood that has lower commercial value, forest biomass is typically harvested as a byproduct of other timber harvest operations. Biomass heating provides markets for lower value wood, which enables healthy and profitable forest management.[ citation needed ]
On a large scale, the use of agricultural biomass removes agricultural land from food production, reduces the carbon sequestration capacity of forests that are not managed sustainably, and extracts nutrients from the soil. Combustion of biomass creates air pollutants and adds significant quantities of carbon to the atmosphere that may not be returned to the soil for many decades. [8] The time delay between when biomass is burned and the time when carbon is pulled from the atmosphere as a plant or tree grows to replace it is known as carbon debt. The concept of carbon debt is subject to debate. Actual carbon impacts may be subject to philosophy, scale of harvest, land type, biomass type (grass, maize, new wood, waste wood, algae, for example), soil type, and other factors. [9]
Using biomass as a fuel produces air pollution in the form of carbon monoxide, NOx (nitrogen oxides), VOCs (volatile organic compounds), particulates and other pollutants, in some cases at levels above those from traditional fuel sources such as coal or natural gas. [10] [11] Black carbon – a pollutant created by incomplete combustion of fossil fuels, biofuels, and biomass – is possibly the second largest contributor to global warming. [12] In 2009 a Swedish study of the giant brown haze that periodically covers large areas in South Asia determined that it had been principally produced by biomass burning, and to a lesser extent by fossil-fuel burning. [13] Researchers measured a significant concentration of 14C, which is associated with recent plant life rather than with fossil fuels. [14] Modern biomass burning appliances dramatically reduce harmful emissions with advanced technology such as oxygen trim systems. [15]
On combustion, the carbon from biomass is released into the atmosphere as carbon dioxide (CO2). The amount of carbon stored in dry wood is approximately 50% by weight. [16] When from agricultural sources, plant matter used as a fuel can be replaced by planting for new growth. When the biomass is from forests, the time to recapture the carbon stored is generally longer, and the carbon storage capacity of the forest may be reduced overall if destructive forestry techniques are employed. [17] [18] [19] [20]
The forest biomass-is-carbon-neutral proposal put forward in the early 1990s has been superseded by more recent science that recognizes that mature, intact forests sequester carbon more effectively than cut-over areas. When a tree's carbon is released into the atmosphere in a single pulse, it contributes to climate change much more than woodland timber rotting slowly over decades. [21] Some studies indicate that "even after 50 years the forest has not recovered to its initial carbon storage" and "the optimal strategy is likely to be protection of the standing forest". [22] Other studies show that carbon storage is dependent upon the forest and the use of the harvested biomass. Forests are often managed for multiple aged trees with more frequent, smaller harvests of mature trees. These forests interact with carbon differently than mature forests that are clear-cut. Also, the more efficient the conversion of wood to energy, the less wood that is used and shorter the carbon cycle will be. [23]
The oil price increases since 2003 and consequent price increases for natural gas and coal have increased the value of biomass for heat generation. Forest renderings, agricultural waste, and crops grown specifically for energy production become competitive as the prices of energy dense fossil fuels rise. Efforts to develop this potential may have the effect of regenerating mismanaged croplands and be a cog in the wheel of a decentralized, multi-dimensional renewable energy industry. Efforts to promote and advance these methods became common throughout the European Union through the 2000s. In other areas of the world, inefficient and polluting means to generate heat from biomass coupled with poor forest practices have significantly added to environmental degradation.
A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.
Gasification is a process that converts biomass- or fossil fuel-based carbonaceous materials into gases, including as the largest fractions: nitrogen (N2), carbon monoxide (CO), hydrogen (H2), and carbon dioxide (CO2). This is achieved by reacting the feedstock material at high temperatures (typically >700 °C), without combustion, via controlling the amount of oxygen and/or steam present in the reaction. The resulting gas mixture is called syngas (from synthesis gas) or producer gas and is itself a fuel due to the flammability of the H2 and CO of which the gas is largely composed. Power can be derived from the subsequent combustion of the resultant gas, and is considered to be a source of renewable energy if the gasified compounds were obtained from biomass feedstock.
Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fuels include wood, charcoal, peat, coal, hexamine fuel tablets, dry dung, wood pellets, corn, wheat, rice, rye, and other grains. Solid fuels are extensively used in rocketry as solid propellants. Solid fuels have been used throughout human history to create fire and solid fuel is still in widespread use throughout the world in the present day.
Wood fuel is a fuel such as firewood, charcoal, chips, sheets, pellets, and sawdust. The particular form used depends upon factors such as source, quantity, quality and application. In many areas, wood is the most easily available form of fuel, requiring no tools in the case of picking up dead wood, or few tools, although as in any industry, specialized tools, such as skidders and hydraulic wood splitters, have been developed to mechanize production. Sawmill waste and construction industry by-products also include various forms of lumber tailings. About half of wood extracted from forests worldwide is used as fuelwood.
A fossil fuel power station is a thermal power station which burns a fossil fuel, such as coal, oil, or natural gas, to produce electricity. Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy, which then operates an electrical generator. The prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating gas engine. All plants use the energy extracted from the expansion of a hot gas, either steam or combustion gases. Although different energy conversion methods exist, all thermal power station conversion methods have their efficiency limited by the Carnot efficiency and therefore produce waste heat.
Bioenergy is a type of renewable energy that is derived from plants and animal waste. The biomass that is used as input materials consists of recently living organisms, mainly plants. Thus, fossil fuels are not regarded as biomass under this definition. Types of biomass commonly used for bioenergy include wood, food crops such as corn, energy crops and waste from forests, yards, or farms.
Pellet fuels are a type of solid fuel made from compressed organic material. Pellets can be made from any one of five general categories of biomass: industrial waste and co-products, food waste, agricultural residues, energy crops, and untreated lumber. Wood pellets are the most common type of pellet fuel and are generally made from compacted sawdust and related industrial wastes from the milling of lumber, manufacture of wood products and furniture, and construction. Other industrial waste sources include empty fruit bunches, palm kernel shells, coconut shells, and tree tops and branches discarded during logging operations. So-called "black pellets" are made of biomass, refined to resemble hard coal and were developed to be used in existing coal-fired power plants. Pellets are categorized by their heating value, moisture and ash content, and dimensions. They can be used as fuels for power generation, commercial or residential heating, and cooking.
A pellet stove is a stove that burns compressed wood or biomass pellets to create a source of heat for residential and sometimes industrial spaces. By steadily feeding fuel from a storage container (hopper) into a burn pot area, it produces a constant flame that requires little to no physical adjustments. Today's central heating systems operated with wood pellets as a renewable energy source can reach an efficiency factor of more than 90%.
Renewable heat is an application of renewable energy referring to the generation of heat from renewable sources; for example, feeding radiators with water warmed by focused solar radiation rather than by a fossil fuel boiler. Renewable heat technologies include renewable biofuels, solar heating, geothermal heating, heat pumps and heat exchangers. Insulation is almost always an important factor in how renewable heating is implemented.
In the context of energy production, biomass is matter from recently living organisms which is used for bioenergy production. Examples include wood, wood residues, energy crops, agricultural residues including straw, and organic waste from industry and households. Wood and wood residues is the largest biomass energy source today. Wood can be used as a fuel directly or processed into pellet fuel or other forms of fuels. Other plants can also be used as fuel, for instance maize, switchgrass, miscanthus and bamboo. The main waste feedstocks are wood waste, agricultural waste, municipal solid waste, and manufacturing waste. Upgrading raw biomass to higher grade fuels can be achieved by different methods, broadly classified as thermal, chemical, or biochemical.
Miscanthus × giganteus, also known as the giant miscanthus, is a sterile hybrid of Miscanthus sinensis and Miscanthus sacchariflorus. It is a perennial grass with bamboo-like stems that can grow to heights of 3–4 metres (13 ft) in one season. Just like Pennisetum purpureum, Arundo donax and Saccharum ravennae, it is also called elephant grass.
Renewable energy in Finland increased from 34% of the total final energy consumption (TFEC) in 2011 to 48% by the end of 2021, primarily driven by bioenergy (38%), hydroelectric power (6.1%), and wind energy (3.3%). In 2021, renewables covered 53% of heating and cooling, 39% of electricity generation, and 20% of the transport sector. By 2020, this growth positioned Finland as having the third highest share of renewables in TFEC among International Energy Agency (IEA) member countries.
Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees, branches, logging residues, stumps, roots, and wood waste.
A wood-burning stove is a heating or cooking appliance capable of burning wood fuel, often called solid fuel, and wood-derived biomass fuel, such as sawdust bricks. Generally the appliance consists of a solid metal closed firebox, often lined by fire brick, and one or more air controls. The first wood-burning stove was patented in Strasbourg in 1557. This was two centuries before the Industrial Revolution, so iron was still prohibitively expensive. The first wood-burning stoves were high-end consumer items and only gradually became used widely.
Biomass briquettes are a biofuel substitute made of biodegradable green waste with lower emissions of greenhouses gases and carbon dioxide than traditional fuel sources. This fuel source is used as an alternative for harmful biofuels. Briquettes are used for heating, cooking fuel, and electricity generation usually in developing countries that do not have access to more modern fuel sources. Biomass briquettes have become popular in developed countries due to the accessibility, and eco-friendly impact. The briquettes can be used in the developed countries for producing electricity from steam power by heating water in boilers.
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy, such as nuclear energy.
Bioenergy with carbon capture and storage (BECCS) is the process of extracting bioenergy from biomass and capturing and storing the carbon dioxide (CO2) that is produced.
Maine Energy Systems (MESys) was founded in summer 2008 by Les Otten, Dutch Dresser, and others to aid in the transition to alternative energy in the northeastern United States. The company delivers wood pellets in bulk and sells fully automated wood pellet boilers for hydronic heating. MESys has been involved in numerous academic studies, work with political groups concerned with the environmental and economic aspects of residential and light commercial heating, and works with American regulatory bodies concerned with the safety of heating appliances.
Pellet heating is a heating system in which wood pellets are combusted. Other pelletized fuels such as straw pellets are used occasionally. Today's central heating system which run on wood pellets as a renewable energy source are comparable in operation and maintenance of oil and gas heating systems.
A pellet boiler is a heating system that burns wood pellets. Pellet boilers are used in central heating systems for heat requirements from 3.9 kW (kilowatt) to 1 MW (megawatt) or more. Pellet central heating systems are used in single family homes, and in larger residential, commercial, or institutional applications. Pellet boiler systems run most efficiently at full load and can usually be regulated down to 30% of full load. Since the warm up phase of pellet boilers usually takes longer than for oil or gas firing systems, short burning phases have negative effects on the fuel efficiency. In order to improve energy efficiency and reduce harmful emissions, pellet boilers are usually combined with buffer systems, such as insulated water tanks.
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