For several years, we have been hearing about greenhouse gases (GHGs) and their impact on climate change. Recently, numerous solutions have emerged to reduce GHG emissions.
One increasingly discussed solution is grain drying using biomass. Subsidies are currently available in Quebec and Canada to accelerate its adoption. But beyond this new technology, what is the real story?
In this article, we will present elements to help you better understand what biomass is, its advantages for grain drying, its economic value, and its agro-environmental impact.
As they say, by thoroughly exploring a topic, we can truly understand it!
What is Biomass?
Biomass is organic material of plant origin that can be used as an energy source. It includes a wide variety of materials, such as wood, agricultural residues, and even certain crops specifically grown for energy production. Among the main types of biomass are:
Wood and forestry residues, such as logs, chips, wood pellets, sawdust, and other residues from the forestry industry.
Agricultural residues, like straw, corn stalks, corn bran, sugarcane bagasse, rice husks, etc.
Energy crops, like plants specifically grown for energy production, such as miscanthus, switchgrass, and fast-growing trees like poplars and willows.
For example, switchgrass has a yield capacity of 8 to 16 tons per hectare in Quebec, potentially up to 20 tons per hectare when intensively cultivated under ideal conditions. With an energy value of 17 MJ/kg of dry matter, switchgrass compares to forest biomass, which has an energy value between 12 and 18 MJ/kg.
For more details on growing switchgrass, consult the "Switchgrass Production Guide" produced by the Quebec Network of Bio-Industrial Plants (RPBQ) published in January 2018.
Besides switchgrass, other crops are also attracting interest. Notably, the cultivation of hemp for processing hemp fiber into pellets (blog on hemp, Innofibre).
What Are the Benefits of Drying Corn with Biomass?
Drying corn with biomass offers several economic and environmental benefits, including significantly reducing energy costs, the possibility of producing one's own biomass, the agronomic value of ashes (NPK), stimulating the local economy, and reducing environmental impact.
Economic Advantages
Reducing energy costs is particularly appreciated. For example, converting propane to biomass for a grain dryer can reduce the energy bill by 80%. It also stabilizes drying costs since the price of biomass is generally more stable than fossil fuels. However, the cost of acquiring a biomass heating system is relatively high.
Modern biomass furnace systems are increasingly efficient and can be adapted for various uses, such as grain drying and heating agricultural buildings (chicken coops, garages, etc.).
Farmers can also use local raw materials to produce energy, reducing their dependence on imported energy sources. They can, for example, valorize forest biomass, crop residues, or even grow plants specifically intended for biomass production.
Using local products reduces transportation costs while stimulating the local economy and reducing the environmental footprint.
Ease and Efficiency of Drying
Contrary to what one might think, biomass drying systems have greatly refined over the years. Today, it is possible to have a fully automated furnace, from biomass feeding to ash management. These 100% automated systems compete perfectly with traditional propane and natural gas systems.
Historically, biomass furnaces used a heat exchanger to transport the produced energy to the grain dryer. While these heat exchanger systems have their place in farm buildings (chicken coops, garages, etc.), they are not suitable for grain dryers.
Since grain drying requires high heating power and fast operation, companies like Triple Green Products have developed furnaces specifically designed for this purpose. For example, the BioDryAir by Triple Green Products is a furnace without a heat exchanger, where the output from the combustion chamber (at nearly 2000 degrees Celsius) is mixed with outside air and directed to the grain dryer.
The air delivered to the dryer (at nearly 400 degrees Celsius) is mixed with the air pushed by the dryer's ventilation system (with the burners off) to reach the desired heating temperature (typically between 170 and 220 degrees Fahrenheit). To date, only direct heating furnace systems are suitable for grain dryers.
Stimulating the Rural Economy and Reducing the Environmental Footprint
In the coming years, a new economy will clearly develop around biomass. The availability of fossil fuels will become increasingly difficult, and biomass fits perfectly as a replacement energy source. This new economy will stimulate the development of infrastructure for biomass production and management and create jobs in various rural areas of Quebec.
Biomass is considered a renewable energy source. When burning biomass, the CO2 released is generally balanced by that absorbed by plants during their growth, contributing to a net reduction in GHG emissions.
Using agricultural or forestry residues for biomass production allows valorizing waste that would otherwise decompose. This generates GHGs without converting the energy value (e.g., methane is the largest contributor to GHGs from biomass decomposition).
Agronomic Advantages
Ashes resulting from biomass combustion can be used as soil amendments to improve soil fertility, closing the nutrient cycle and enhancing soil quality. Crops like switchgrass have also shown notable benefits for soil improvement.
Propane vs. Forest Biomass Energy Value
Comparing the energy value of propane and forest biomass highlights the significant differences between these two fuel sources in terms of energy efficiency.
Propane Energy Value
Propane is a hydrocarbon with high energy density. The lower calorific value (LHV) and higher calorific value (HHV) are commonly used to express the energy released during combustion.
HHV of propane: about 55 MJ/kg
LHV of propane: about 46 MJ/kg
LHV is generally used in energy calculations to account for energy loss due to water vapor formed during combustion. It means a part of the available energy is used to evaporate the combustion water. By using LHV, you work with the available energy.
Forest Biomass Energy Value
Forest biomass has a lower energy density than propane. The energy value of biomass can vary depending on its composition and moisture content. Here are some typical values for dried forest biomass:
HHV of forest biomass: about 13-20 MJ/kg
LHV of forest biomass: about 12-18 MJ/kg
The energy value of biomass depends on its water content. For dried biomass (about 10-20% moisture), these values can be used as references.
Energy Value Comparison
Energy Source | HHV (MJ/kg) | LHV (MJ/kg) |
Propane | 55 | 46 |
Forest Biomass | 13-20 | 12-18 |
Comparative Analysis
Propane has a significantly higher energy value (46 MJ/kg) than forest biomass (15-18 MJ/kg), meaning it is more efficient for producing energy per unit of weight. In comparison, it will take burning three times more biomass weight to produce the same amount of energy.
Propane vs. Forest Biomass Energy Cost
Comparing the energy cost of propane to that of forest biomass requires examining both the cost per energy unit and the efficiency of using each fuel. Here is a detailed analysis of these costs:
Propane Energy Cost
The cost of propane varies depending on local markets, seasons, and quantities purchased. Generally, the price of propane can be estimated as follows:
Propane price: about $0.40 to $0.60/L
LHV of propane: 46 MJ/kg
To convert the price to cost per energy unit, we need to know the density and energy content of propane.
Density of liquid propane: about 0.515 kg/L
LHV of propane: 46 MJ/kg
Calculation of propane energy cost:
1 liter of propane = 0.515 kg
1 liter of propane = 0.515 kg × 46 MJ/kg ≈ 23.69 MJ
If the price of propane is $0.50/L (an average value),
Cost per MJ = $0.50 / 23.69 MJ ≈ $0.021 per MJ
Forest Biomass Energy Cost
The cost of forest biomass depends on several factors, including the type of biomass, its moisture content, local availability, transportation, and preparation costs. An average estimate could be as follows:
Forest biomass price: about $60 to $90/ton
LHV of forest biomass: 12-18 MJ/kg
To simplify, let's use an average value:
LHV of biomass: 12 MJ/kg
Calculation of biomass energy cost:
1 metric ton of biomass = 1000 kg × 12 MJ/kg = 12,000 MJ
If the price of biomass is $60 CAD per ton,
Cost per MJ = $60/ton / 12,000 MJ ≈ $0.004 per MJ
Comparative Analysis
Energy Source | Cost per MJ (CAD) |
Propane | About $0.021 |
Wood Chips at $60/ton | About $0.004 |
Wood Chips at $90/ton | About $0.0075 |
Combustion Efficiency:
Propane combustion systems are generally more efficient (about 85% to 95%) than biomass systems (about 60% to 80%, with BDA being 95% to 97%), which can influence the actual costs to obtain the same amount of useful heat.
Only biomass furnaces specially designed for grain drying can achieve performance equal to traditional propane systems.
The efficiency of biomass furnaces is greatly influenced by the moisture content in the biomass used. The drier the product, the higher the energy value.
Type of Biomass
Type of Biomass | Energy Value (MJ/kg) | % Moisture | Cost ($/ton) |
Moist Wood Chips | 12.0 | 33% | 60 |
Dry Wood Chips | 15.0 | 13% | 100 |
Switchgrass | 17.0 | 13% | 48-68 |
Wood Pellets | 18.0 | 8% | 225 |
Comparative Table of Biomass Energy Values According to Moisture Content
Total Cost of Use:
- Propane: More expensive per energy unit, but easier to manage and burn efficiently.
- Biomass: Cheaper per energy unit. Often requires more complex combustion systems and a bit more effort for transport management, but once installed, it is no more complicated than propane.
Summary
The energy cost of propane is significantly higher (more than five times) than that of forest biomass when considering the cost per MJ. However, combustion efficiency and infrastructure and management costs must also be considered in the overall cost evaluation.
For applications where simplicity, cleanliness, and efficiency are priorities, propane may be preferred despite its higher energy cost. On the other hand, for sustainable and economical solutions, particularly in rural contexts or large-scale installations, forest biomass could offer significant cost and environmental impact reduction advantages.
What is the Agronomic Value (NPK) of Forest Ashes?
Forest ashes, resulting from the combustion of wood residues and other organic materials, are often used as soil amendments in agriculture and forestry due to their essential nutrient content.
The NPK value (Nitrogen, Phosphorus, Potassium) of forest ashes can vary depending on several factors, including the type of wood burned, combustion temperature, and specific conditions. However, a general estimate of the NPK value of forest ashes is as follows:
Typical Composition of Forest Ashes:
Nitrogen (N): Very low, often less than 1%. Nitrogen is generally volatilized as gas during combustion, leaving the ashes with negligible nitrogen content.
Phosphorus (P2O5): About 1% to 3%. Phosphorus remains as phosphate in the ashes and can be used by plants.
Potassium (K2O): About 3% to 8%. Potassium is generally present in relatively high amounts in the ashes and is readily available to plants.
Other Nutrients:
In addition to nitrogen, phosphorus, and potassium, forest ashes contain other beneficial nutrients for plants, such as:
Calcium (CaO): 20% to 30% or more. Calcium is a major constituent of ashes and helps neutralize soil acidity.
Magnesium (MgO): 1% to 5%. Magnesium is important for photosynthesis.
Trace Elements: Ashes may also contain traces of micronutrients, such as iron, manganese, zinc, and copper, which are essential for plant growth.
Advantages of Forest Ashes:
Although forest ashes have low nitrogen content, they are a valuable source of phosphorus, potassium, and calcium, making them useful as soil amendments. Their high calcium content can help increase the pH of acidic soils, thus improving nutrient availability for plants.
However, it is important to determine the appropriate application rate to avoid over-fertilization and nutrient imbalances. A prior soil analysis is recommended. Consult your agronomist!
Conclusion
In conclusion, although the acquisition cost of a biomass dryer is relatively high, if your initial energy consumption exceeds $60,000 per year, the savings achieved through biomass will quickly make the investment worthwhile.
Plant biomass (forest or cultivated) is a very promising avenue for agriculture, even a green revolution, whether for grain drying or heating buildings.
Unlike propane, the energy cost of biomass is 3 to 5 times lower and fits perfectly into a greener energy transition. Producers can thus free themselves from fossil fuels and even produce their own biomass, allowing them to achieve energy self-sufficiency (circular economy) for drying their crops.
Curious about this revolution? Want to discuss it? Contact us!