Harnessing the Power of Biomass: Renewable Energy From Grasses And Woody Plants
There is a lot of talk about the promising potential of biomass energy how we can use grasses and woody plants to harness to generate power, heat, and biofuels and create sustainable, renewable energy solutions that are better for our planet and its resources. Learn more about how biomass crops like King Grass, Willow and Paulownia are transforming the clean energy space.
Biomass represents a type of renewable energy sourced from organic substances that are predominantly plant based. This category encompasses any fuel-compatible material derived from plants, like timber, cultivated crops, farm byproducts, grass, and even urban waste.
Energy can be derived from biomass through a range of techniques including burning, gasifying, processing through anaerobic digestion, and pyrolyzing. Combustion entails burning the biomass to generate heat, which can be utilized for electricity generation or space heating. Gasification requires heating the biomass under high temperatures with limited oxygen to create a fuel-ready gas. In anaerobic digestion, organic matter decomposes without oxygen, yielding biogas that can be used for producing electricity or as a heating fuel. Pyrolysis is the process of heating the biomass without oxygen at high temperatures, resulting in liquid biofuels or a fuel-compatible gas.
Renewable Energy
Harnessing renewable energy from biomass entails employing primarily plant-based organic substances to generate electricity, heat, and other energy forms. Biomass serves as a versatile renewable energy resource.
- Direct combustion: Biomass can be incinerated directly, yielding heat or steam. This can be harnessed to produce electricity or supply heat for industrial operations, structures, and residences.
- Co-firing: Biomass can be incinerated directly, yielding heat or steam. This can be harnessed to produce electricity or supply heat for industrial operations, structures, and residences.
- Gasification: Biomass can be transformed into a gaseous form, serving as fuel in power generation facilities or industrial procedures.
- Anaerobic digestion: Organic substances like farm waste or animal dung can be decomposed without the presence of oxygen, producing biogas. This biogas can be utilized to generate electricity or provide heat.
- Biofuels: Biomass can be transformed into liquid biofuels like ethanol and biodiesel, serving as effective fuels for transportation.
Renewable energy from biomass is seen as a sustainable and environmentally conscious alternative to fossil fuels due to its renewable status and its potential to reduce greenhouse gas emissions. However, it carries certain potential drawbacks, including the need for large land areas for growing biomass crops and potential negative impacts on soil health and biodiversity. Therefore, it's essential to carefully evaluate the environmental, societal, and economic consequences of utilizing biomass as a renewable energy source.
Biomass Tree Crops
Tree crops are the most grown. representing 70% of the global biomass market due to the high plant to heat (BTU) conversion rate. Simply stated, biomass tree crops require far less plant mass compared to grass and vegetable to achieve a consistent burn rate.
Advantages
- High plant to heat conversion rate
- More profitable per acre
- New plant regeneration from cut stumps
- After harvest regeneration grows twice the plant matter
- Repeating cycles of new plant from stump regeneration
Disadvantages
- Harder to break down into furnace material
- Longer growth cycle (8 to 12 years)
- Expensive to plant
Hybrid Poplar
Classified as a softwood, hybrid poplar trees are fast growing and adaptable to a wide variety of soils and climates. In perfect soil (loose, well-fertilized loam) and climate (regular rainfall, ample sunshine, and temperatures around 80 degrees Fahrenheit), poplar trees can grow 5 feet or more in a year. Hybrid poplar trees are a popular choice for biomass tree crops because they grow quickly and can be harvested for energy production on a relatively short rotation cycle.
- Choose a suitable location: Hybrid poplars thrive in well-drained soils with abundant sunlight. While they can withstand various soil types, they favor those with a pH level ranging from 5.5 to 7.5. Steer clear of areas susceptible to flooding or where water tends to pool.
- Obtain and plant the cuttings: Hybrid poplars are typically grown from stem cuttings, which can be obtained from a reputable nursery or propagated from existing trees. Cuttings should be planted in the early spring, after the last frost, in rows spaced about 10 feet apart. Cuttings should be planted about 6-8 feet apart within the rows.
- Provide proper care: Hybrid poplars require regular watering and fertilization during the first few years of growth to establish strong root systems. They also require regular pruning to encourage strong, straight growth and to remove any diseased or damaged branches.
- Harvest and regrow: After approximately 3-4 years of development, hybrid poplars are ready for biomass harvesting. The trees should be trimmed down to about 2-3 feet above ground level, which allows them to sprout anew and provide several harvests during their life cycle. When the trees reach an age of around 20-25 years, they should be substituted with fresh cuttings to sustain a constant rotation cycle.
Growing hybrid poplar as a biomass tree crop can be a sustainable and profitable venture for landowners interested in renewable energy production.
Harvesting Biomass For Fuel Video
Paulownia
Paulownia, also known as an empress tree, is an extremely fast-growing tree native to China. It is gaining in popularity as a biomass crop from its adaptability to grow well in parts of the United States and Europe. The calorific value of Paulownia is half that of most hardwoods, but low transportation and fiber break down costs lowers transportation and handling expenses. Paulownia is generally a branchy tree and as such grows an inordinate amount of biomass around the trunk of each tree.
Paulownia is a rapidly maturing tree species frequently employed for biomass production owing to its high yield, quick rotation timeframe, and adaptability to diverse soil types and weather conditions. Here are some pointers for cultivating Paulownia for biomass:
- Site selection: Choose a site that receives full sun, has well-draining soil, and is sheltered from strong winds. Paulownia is adaptable to various soil types, though it exhibits a preference for mildly acidic soil with a pH range between 5.5 and 6.5.
- Planting: Paulownia can be propagated from seeds or cuttings. If propagating from seeds, sow the seeds in the spring after the last frost. If propagating from cuttings, take cuttings from mature trees in the fall and root them in a well-draining soil mix.
- Soil preparation: Prior to planting, ready the soil by plowing it to a minimum depth of 6 inches and incorporating organic substances like compost or manure to enhance the soil's fertility and structure.
- Fertilization: As Paulownia necessitates ample nutrients for fast growth, regular fertilization is critical. During the growth period, apply a balanced fertilizer with a nitrogen-phosphorus-potassium (NPK) composition of either 10-10-10 or 12-12-12 every 6 to 8 weeks.
- Irrigation: Paulownia requires regular watering, especially during the first two years of growth. Water deeply once a week or more often during hot, dry weather.
- Pest and disease control: Paulownia is relatively resistant to pests and diseases, but it can be susceptible to root rot and leaf spot. To prevent these problems, avoid overwatering and provide good air circulation around the trees.
- Harvesting: Paulownia can be harvested for biomass after 3-5 years of growth, depending on the desired size of the trees. Cut the trees at ground level and remove the branches before chipping the wood for use as biomass.
Overall, growing paulownia for biomass can be a profitable and sustainable enterprise, but it requires careful planning and management to ensure success.
American Basswood
Basswood is native to the Great Lake basin of North America where it thrives in generally continental-cold winters, warm summers, and humid to subhumid moisture conditions. American basswood grows fast, averaging 5 feet or more a year in its juvenile stage, which spans from the second to its tenth year of growth when it stands 40 feet or more in height with an average caliper of 8 inches. Fast growth and decent wood volume make this tree an ideal candidate for biomass tree plantations. It is comparable to Paulownia in any ways but costs far less to procure and plant.
American basswood is relatively new to the biomass space, having been overlooked for the more exotic tree varieties. However, this forgotten tree is native to much of the prime land that has been lying fallow for several decades around the Great Lakes. Seed is cheap, plentiful and the tree grows fast in its natural habitat. Unlike some woody biomass varieties, basswood is truly a “plant-and-forget” tree requiring no maintenance during its growing cycles. Basswood seeds are best propagated as 1, 2 or 3 foot tree seedlings for transplant in the field. Tree seedlings are spaced 2 to 3 feet apart along straight, parallel rows or along a looping spiral where trees are spaced alternatively, both sides of an imaginary line that forms the spiral. Spiraled plantations grow biomass about 20% faster.
Willow Wood
Willow wood is rapidly coming to the fore as a viable bioenergy crop grown as a short rotation tree crop for biomass. In the wild, will grows extremely fast on wetlands where the water table is high through the summer months. A cross-country breeding program has thus far produced willow clones that have twice the caliper mass of wild wood. Grown as a high-density thin wood, it is easily harvestable by current poplar biomass harvesters, which convey plant matter into parallel container trucks. The advantage of willow wood is that it has a higher BTU than hybrid poplar, paulownia and basswood.
Hybrid willow clones are banded in groups of 5 and spaced 2 feet apart in linear or spiral rows depending on the configuration of the plantation. In year 5 they are mechanically harvested, delivered and stored in a covered drying facility to cure product. An operation outfitted with a “roll dry drum” will deliver dried product in half the time compared to a “toss and turn” on a concrete floor facility. After harvest, 2 new shoots will grow from the cut stump ends of each tree doubling the output of the plantation. After the second harvest, 3 new shoots triple production, which maximizes harvest cycle to cycle. Willow wood never needs replanting during the life cycle of the plantation.
Biomass Grass Crops
Giant King Grass is quickly being recognized as one of the best grass crops for biomass production in tropical and sub-tropical regions of the world with more than 110 days of sunshine and a minimum of 30 inches of rain per year. Fertilizer requirements are modest, and pesticide is not required.
Giant King Grass exhibits extraordinary rapid growth. Unlike other crops like miscanthus, switchgrass, and bamboo which have considerably lower yields and aren't ready for harvesting until their second, third, or even fourth year of growth, this grass is a short-rotation crop that can be harvested within its first year. Once Giant King Grass is sown, it can be harvested for biogas production when it reaches 3 feet in height after just 40 days, with subsequent harvests every 25 to 30 days. For other uses such as pellet or biofuel production, it's harvested when it attains a height of 13 feet after 195 days, followed by successive harvests every 120 days. This grass's impressive growth rate can provide a consistent biomass supply throughout the year.
The yield of this tropical grass is 167 tons per acre of wet grass with 70% moisture content; dried, the grass yields 45 tons per acre.
Biomass Vegetable Crops – Ethanol Production
Corn, thanks to its plentiful supply and straightforward transformation into ethanol, is a favored crop for biomass-based ethanol production in the United States. Unlike sugarcane, in which squeezed sugar water can be directly fermented, corn starch must be cooked with alpha and enzymes to convert the starch to simple sugars. Ethanol yield per acre averages 462 gallons per acre from a feedstock yield of 165 bushels per acre while an acre of sugarcane can produce an approximate 35 ton yield, resulting in about 560 gallons of sugarcane ethanol.
The availability of sugar cane stock is limited due to restrictions from climate and limited acreage for production (about 5,000 acres) while in the United Sates alone, approximately 100 million acres are under production with corn feedstock.