USE OF SOLID BIOMASS IN AGRICULTURAL GREENHOUSES
Greenhouse heating with biomass is an ecological solution that will provide long term financial benefits for the greenhouse operator. In many cases, the greenhouse will produce sub-products that can be used as fuel for the biomass heating system.
In Northern countries with cold weather like Canada, heating a greenhouse requires large amounts of energy. Therefore, heating a greenhouse with fossil fuels will end up with a huge heating bill and a huge carbon footprint. Biomass heating can provide a cost-effective alternative that is also carbon-neutral.
In many cases, the biomass boiler will even be able to burn some of the by-products of the greenhouse, meaning free heating fuel for the owner.
Greenhouses with automated lights present a challenge for heating as they have a strong peak demand for heat at the moment when the lights go out. This is not really the case with the newest LED systems, but is a big problem for greenhouses with older electric lightbulbs which generate large amounts of heat.
Biomass boilers are quite expensive compared to other types of heating devices. Therefore, installing a huge biomass boiler to be used at full capacity only for such an energy peak is usually not cost-effective.
Generally, the best investment / savings ratio for greenhouse heating with biomass will be for a biomass boiler that will cover around 50 to 60% of the output needed during the daily peak demand. As the peak represents only a small part of the day, such a biomass boiler will cover between 80 and 90% of the annual heat demand of the greenhouse.
To cover the needs during the heat demand peak, it is possible to install a huge buffer tank filled with water that will store enough heat to be able to go through the heat demand peak. The heating system will then be able to meet the demand during the peak, and reheat the buffer tank during the rest of the day.
Biomass Energy for Greenhouses
Biomass is fuel that is developed from organic materials, a renewable and sustainable source of energy used to create electricity or other forms of power. Bioenergy is carbon neutral electricity generated from renewable organic waste that would otherwise be dumped in landfills, openly burned, or left as fodder for forest fires. Biomass can be made from agricultural and forestry residues and some industrial wastes and crops grown solely for energy purposes.
Biomass System Design
Biomass systems are customized to the grower’s needs and conditions in order to fully utilize the advantages of the biomass concept: auger sizing, types of screening used, burn capabilities and most importantly the size of the boiler required. Biomass boiler system manufacturers generally size the units to 60 percent of the total capacity needed to heat the greenhouse in question.
Components of Biomass Systems
Regardless of the end user being served, large-scale biomass systems generally require a similar integrated network of components, the complexity of which will vary according to the heat output and the type of fuel. The following is a brief description of these components. The storage bin needs to be sized in order to ensure an adequate supply of fuel during peak demand and designed to function in sync with delivery vehicles.
Storage of Biomass
When storing biomass, greenhouse operators should consider, without limitation, the following:
- Biomass is bulky and requires large storage facilities.
- Biomass has a higher moisture content. There is more shipping weight and lower heating efficiency with biomass.
- Biomass will absorb moisture if left in the open. In most cases, when the outer layer of the pile is wet, the interior of the pile remains relatively dry.
- Biomass may spontaneously combust under the wrong conditions:
- Material was too wet when piled.
- There is a large variation in particle size, creating pockets of trapped air.
- Compacted materials prevented heat dissipation from the storage pile.
- There is a potential for odors when fuel source breaks down.
- There is a potential for wind-blown dust and debris off the storage piles.
- There is a potential for runoff or leachate from the storage facility. This must not be allowed to reach surface or groundwater in a manner that will impact the environment.
Ash Disposal
There are two types of ash:
- ash remaining in the combustion chamber
- fly ash (ash collected from the cyclone and smoke stack)
However, ash must be disposed of responsibly after the combustion of biomass. Ash remaining in the combustion chamber may be disposed of in landfill or incorporated into the soil as a soil amendment. Fly ash can be considered hazardous and should be disposed of in a facility approved to receive this type of waste. If the material remaining in the ash chambers is composed of more than 10% unburned fuel, it should be disposed of at a landfill site.
Types of biomass
Agricultural waste – waste, other than sewage, resulting from farm operations, including animal husbandry and, where a farm operation is carried on in respect of food packing, food preserving, animal slaughtering or meat packing, includes the waste from such operations.
Biomass – materials organic in origin that can be used as fuel (e.g., wood, straw, stover, husks, grains and even manure and bio-degradable wastes that can be burned as fuel).
Biofuel – fuel derived from biomass, including liquid and gaseous fuels such as ethanol and biodiesel, produced from agricultural products such as corn, soybeans, flaxseed, canola and sugar cane.
Energy crop – crop grown for the production of fuel wherein the whole plant is used or processed for this purpose.
Processed organic waste – waste that is predominantly organic in composition and has been treated by aerobic or anaerobic digestion, or other means of stabilization, and includes sewage residue from sewage works that is subject to the provisions of the Ontario Water Resources Act.
Waste biomass – organic matter that is derived from a plant or an animal, that is available on a renewable basis and that is any of:
- waste from harvesting or processing agricultural products or forestry products
- waste resulting from the rendering of animals or animal by-products
- solid or liquid material that results from the treatment of wastewater generated by a manufacturer of pulp, paper, recycled paper or paper products, including corrugated cardboard
- water from food processing and preparation operations
- wood waste
Benefits of heating agricultural greenhouses with solid biomass
- Renewable Energy Source: Solid biomass, derived from organic materials such as wood, agricultural residues, or energy crops, is renewable and can be sustainably harvested or cultivated, reducing reliance on finite fossil fuels.
- Carbon Neutrality: When managed sustainably, biomass combustion releases carbon dioxide (CO2) that was recently captured by growing plants, maintaining a closed carbon cycle and mitigating net greenhouse gas emissions.
- Cost-Effectiveness: Biomass fuels can often be locally sourced, reducing transportation costs and offering a cost-effective alternative to fossil fuels, especially in regions with abundant biomass resources.
- Enhanced Energy Security: Utilizing locally available biomass resources enhances energy independence and resilience for greenhouse operations, reducing vulnerability to fluctuations in fossil fuel prices and supply disruptions.
- Waste Utilization: Biomass heating can utilize agricultural residues or forestry by-products that would otherwise be considered waste, offering an opportunity for waste reduction and resource efficiency.
Challenges and Considerations
- Efficiency and Emissions: Efficient combustion technologies and proper maintenance are essential to minimize emissions of air pollutants such as particulate matter, nitrogen oxides (NOx), and volatile organic compounds (VOCs) associated with biomass combustion.
- Fuel Quality and Supply Chain: Ensuring consistent fuel quality, proper storage, and reliable supply chains are crucial to maintaining efficient and reliable biomass heating systems.
- Environmental Impacts: While biomass combustion can be carbon-neutral when managed sustainably, improper practices such as deforestation or unsustainable harvesting can lead to habitat destruction, biodiversity loss, and increased greenhouse gas emissions.
- Regulatory Compliance: Compliance with emissions standards, air quality regulations, and sustainability criteria may impose additional requirements and costs on biomass heating systems, necessitating careful planning and regulatory adherence.
Potential of biomass use in agricultural greenhouses
- Technological Innovation: Continued research and development in biomass combustion technologies, such as advanced boilers, combined heat and power (CHP) systems, and biomass pelletization, can improve efficiency, reduce emissions, and enhance the viability of biomass heating for greenhouse applications.
- Integrated Systems: Integrating biomass heating with other renewable energy sources such as solar thermal, geothermal, or heat recovery systems can further enhance energy efficiency and resilience while reducing environmental impacts.
- Sustainable Biomass Management: Implementing sustainable biomass harvesting and land management practices, including afforestation, agroforestry, and crop residue management, can ensure the long-term viability of biomass resources for heating applications while enhancing ecosystem services and biodiversity.
- Policy Support: Policy frameworks that incentivize renewable energy deployment, promote sustainable biomass utilization, and support research and development initiatives can accelerate the adoption of biomass heating in greenhouse operations and contribute to climate change mitigation efforts.
Utilizing solid biomass for heating greenhouses offers a sustainable solution to meet the energy needs of agricultural production while reducing environmental impacts and enhancing energy security. Despite challenges related to efficiency, emissions, and sustainability, technological innovation, integrated system approaches, and supportive policy frameworks hold promise for advancing the viability and scalability of biomass heating in greenhouse operations. By harnessing the potential of solid biomass, greenhouse growers can contribute to a more sustainable and resilient agricultural sector while mitigating climate change impacts.
