Supply and Energy Use of Lignocellulosic Biomass. Learning Diary. Mona Nazari

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1 Supply and Energy Use of Lignocellulosic Biomass Learning Diary Mona Nazari Dec

2 What is energy? Energy exists freely in nature. Some of them exist infinitely (never run out, called Renewable), the rest have finite amounts (they took millions of years to form, and will run out one day, called Nonrenewable). With this in mind, it is a lot easier to lay any type of energy source in its right place. You will notice that water, wind, sun and biomass (vegetation) are all available naturally and were not formed. The others do not exist by themselves, they were formed. Renewable energy resources are always available to be tapped, and will not run out. This is why some people call it Green Energy What is Biomass? Biomass fuels come from things that once lived: wood products, dried vegetation, crop residues, aquatic plants and even garbage. It is known as 'Natural Material'. Plants used up a lot of the sun's energy to make their own food (photosynthesis). They stored the foods in the plants in the form of chemical energy. As the plants died, the energy is trapped in the residue. This trapped energy is usually released by burning and can be converted into biomass energy. Wood is a biomass fuel. It is renewable. As long as we continue to plant new trees to replace those that were cut down, we will always have wood to burn. Just as with the fossil fuels, the energy stored in biomass fuels came originally from the Sun. It is such a widely utilized source of energy, probably due to its low cost and indigenous nature, that it accounts for almost 15% of the world's total energy supply and as much as 35% in developing countries, mostly for cooking and heating. How is biomass converted into energy? Burning: This is a very common way of converting organic matter into energy. Burning stuff like wood, waste and other plant matter releases stored chemical energy in the form of heat, which can be used to turn shafts to produce electricity. Let's see this simple illustration of how biomass is used to generate electricity. 2

3 1. Energy from the sun is transferred and stored in plants. When the plants are cut or die, wood chips, straw and other plant matter is delivered to the bunker. 2. This is burned to heat water in a boiler to release heat energy (steam). 3. The energy/power from the steam is directed to turbines with pipes. 4. The steam turns a number of blades in the turbine and generators, which are made of coils and magnets. 5. The charged magnetic fields produce electricity, which is sent to homes by cables. Other ways in which organic matter can be converted into energy include: Decomposition: Things that can rot, like garbage, human and animal waste, dead animals and the like can be left to rot, releasing a gas called biogas (also known as methane gas or landfill gas). Methane can be captured by a machine called Microturbine and converted into electricity. Sometimes, animal waste (poop) can also be converted into methane by a machine called 'Anaerobic Digester' Fermentation: Ethanol can be produced from crops with lots of sugars, like corn and sugarcane. The process used to produce ethanol is called gasification. 3

4 Feedstock At present, forestry, agricultural and municipal residues, and wastes are the main feedstocks for the generation of electricity and heat from biomass. In addition, a very small share of sugar, grain, and vegetable oil crops are used as feedstocks for the production of liquid biofuels. Today, biomass supplies some 50 EJ1 globally, which represents 10% of global annual primary energy consumption. This is mostly traditional biomass used for cooking and heating. See Figure 1. Figure 1. Share of bioenergy in the world primary energy mix. Source: based on IEA, 2006; and IPCC, 2007 There are many bioenergy routes which can be used to convert raw biomass feedstock into a final energy product (see Figure 2). Several conversion technologies have been developed that are adapted to the different physical nature and chemical composition of the feedstock, and to the energy service required (heat, power, transport fuel). Upgrading technologies for biomass feedstocks (e.g. pelletisation, torrefaction, and pyrolysis) are being developed to convert bulky raw biomass into denser and more practical energy carriers for more efficient transport, storage and convenient use in subsequent conversion processes. 4

5 Figure 2: Schematic view of the wide variety of bioenergy routes. Source: E4tech, Feedstock production systems can also provide several benefits. For instance, forest residue harvesting improves forest site conditions for planting, thinning generally improves the growth and productivity of the remaining stand, and removal of biomass from over-dense stands can reduce the risk of wildfire. In agriculture, biomass can be cultivated in so-called multifunctional plantations that through well-chosen locations, design, management, and system integration offer extra environmental services that, in turn, create added value for the systems. Global trade in biomass feedstocks (e.g. wood chips, vegetable oils and agricultural residues) and processed bioenergy carriers (e.g. ethanol, biodiesel, wood pellets) is growing rapidly. Transportation Transport biofuels are currently the fastest growing bioenergy sector, receiving a lot of public attention. However, today they represent only 1.5% of total road transport fuel consumption and only 2% of total bioenergy. They are, however, expected to play an increasing role in meeting the demand for road transport fuel, with 2nd generation biofuels increasing in importance over the next two decades. Even under business-as- 5

6 usual scenarios, biofuel production is expected to increase by a factor of 10 to 20 relative to current levels by 2030 (corresponding to a 6-8% average annual growth rate) Biomass Supply Chains and Logistics As was shown in the previous sections, biomass potentials are influenced by the development of the agricultural sector and various sustainability constraints. Additional constraints linked to the collection and distribution of dedicated energy crops and agricultural and forestry residues may further affect the realisable potential. These include: Equipment constraints. Collection methods may vary greatly between developed and developing countries, but also by region in developing countries. Mechanisation of the harvesting process and integration of residue collection may greatly influence the efficiency, but may also require significant investments. Current harvesting methods and practices. Often agricultural residues are burnt before the harvest (e.g. sugar-cane tops and leaves, to facilitate manual harvesting), burnt after harvest, or ploughed back into the field in order to improve soil quality or suppress the growth of weeds. Physical constraints. Steep slopes, wet soils, small size of fields and low-quality infrastructure can make the cropped area inaccessible to mechanical harvesters or may cause harvesting to be more inefficient. Specialised equipment may partially help overcome these constraints. These factors also influence the economics of biomass supply chains. The logistics associated with conventional food crops (such as sugar-cane, corn, rapeseed, and palm oil) and forestry products (such as round wood and pulp chips) are well established and cost-efficient. Experience with these crops can to some extent be applied to the new bioenergy crops, e.g. perennial grasses or fast-growing trees. However, for most field residues, the development of cost-efficient supply chains is a major challenge. The collection, pre-transport processing (such as chipping or baling) and transportation of woody and agricultural residues can add significantly to the overall feedstock costs, as can be seen in Figure 3 for woody biomass. 6

7 Figure 3. Typical cost structures in different countries for wood chips from whole trees, thinnings and forest residues delivered to a plant. Transport distances vary between different studies, typically between kilometres. Short rotation for biomass production Besides conventional forestry, a huge potential for solid biomass production is expected to come from high yielding, coppiceable tree species such as willows (Salix spp.) and poplars (Populus spp.), cultivated in plantations with dense stands and relatively short rotation harvesting cycles of 3-5 years. Short-Rotation Woody Energy Crops (SRWC) The SRWC are fast growing woody plants with a great range of adaptability and good disease resistance. The SRWC considered as bioenergy crops include hardwood species such as poplar (Populus ssp.), willow (Salix spp.), cottonwood (Populus fremontiil.), sweetgum (Liquidambar styraciflua), sycamore (Platanus occidentalis), black locust (Robinia pseudoacacia), silver maple (Acer saccharinum L.), and Eucalyptus. The SRWCs can be grown for other uses also such as paper production and the waste can be utilized for energy. Some of the species of considerable regional importance in the United States are alders (Alnus spp.), mesquite (Prosopis spp.), and the Chinese tallow (Sapium sebiferum) In many countries a specialist poplar and willow planting service provider is available. Before plantation establishment, farmers should analyse if it is economically more viable to use a professional provider for assistance, or to carry out all the planting procedures 7

8 independently, in order to get a good quality SRP plantation with a high yield over its complete life span. Before planting it is necessary to select a plantation design that will be compatible with the planned management and harvesting system to be adopted. For example, the required distances between the plant rows that allow for mechanical weed control and harvesting without damaging the plant stumps. On the other hand, in an area of heavy soil with predictably high moisture content, during harvesting the root systems of SRP crop can perform additional carrying capacity. Environmental assessment Impacts on biodiversity, water, soil and air quality the production and use of biomass for energy can cause harmful environmental impacts in certain cases. These concern mainly biodiversity, soil, and air quality. The production of agricultural biomass can result in negative impacts on soils (e.g. loss of nutrients and soil organic matter, erosion, peatland drainage), water availability and biodiversity. A study in 2013 concluded that considerable potential risks to sustainability from biofuel cultivation exist, particularly risks to soils and to water quality and water availability. The use of agricultural residues (such as straw) can also cause negative impacts on soils (fertility and structure) and on biodiversity if extracted in excessive amounts. On the other hand, the use of waste (for example manure) to produce biogas can significantly reduce methane and other emissions. In the EU, the rules of cross-compliance under the Common Agricultural Policy ensure the implementation of existing environmental requirements and the requirement of maintaining land in good agricultural and environmental condition. An increased production and use of forest biomass for energy can also cause negative environmental impacts. For example, an excessive removal of harvest residues, or the removal of stumps, can harm soil productivity, biodiversity, and water flows. If done sustainably, additional mobilisation of forest biomass can also have positive impacts (e.g. removal of early thinnings beneficial to biodiversity, improvement of forest structure, prevention of fires, pests and diseases, afforestation on eroded land, etc.). Often, such practices incur barriers (such as higher costs) compared to traditional forest management. Estimating heating demand Estimations of the future energy consumption of buildings are becoming increasingly important as a basis for energy management, energy renovation, investment planning, and for determining the feasibility of technologies and designs. Future weather scenarios, 8

9 where the outdoor climate is usually represented by future weather files, are needed for estimating the future energy consumption. To determine the annual energy demand of a building, we require a weather file that describes the typical weather conditions at the building's location, as well as information on the structure and usage of the building. A typical weather file is usually constructed from real, measured data. In figure 4, By extracting past weather result values and heat result values and comparing them to similar future weather forecasting values (temperature, humidity, and so on), this system estimates future heat demand values from weighted averages of heat demand results based on the distances between weather forecasting values and result values in the data. Figure 4: Heat Demand Prediction Concept Estimating a building's peak daily fuel demand The peak daily fuel demand is of considerable interest if you suspect that your building's heating plant is oversized. Overcapacity is often designed-in (thanks to excessive safety margins) and sometimes is made worse by the building having been subsequently insulated and draught-proofed. For example, a building is found to have fixed demand of 9

10 2,100 kwh per week and weather-related demand of 100 kwh per degree day (base temperature: 15.5C). What is its peak daily demand? Assume a worst-case outside air temperature of -1C. 1. The weather-dependent demand on the coldest day is (15.5-(-1))*100 = 1,650 kwh 2. Fixed demand is 2,100/7 = 300 kwh 3. Hence total demand on the coldest day is 1, = 1,950 kwh Biomass and bioenergy potential estimation has been worldwide research highlights in renewable energy field to get comprehensive understand of bioenergy development, especially under the situation of energy crisis. The below figure is a review of analyze the potential of dedicated energy crops, and some also included other feedstocks such as wastes, residues, and forestry (Figure 5). Figure 5: Total biomass potential broken down by feedstock in original studies compared to world energy consumption 10

11 Biomass Production and Carbon Sequestration Perennial crops are highly productive, have a high capacity to sequester C from the atmosphere, cause minimal soil disturbance during their growing season, and accumulate SOC over a year period. Assessment of how much of the C in biomass can be sequestered into the soil is important since most of the C stored in the aboveground biomass is to be utilized for energy production. This means that the release of CO2 from co-firing of biomass does not contribute to the net global CO2 levels since the CO2 released during its utilization was recently removed from the atmosphere. There are two main concerns associated with the effects on the C cycle are the increased atmospheric CO2 due to the use of fossil fuels and the loss of C and soil productivity from agricultural systems. Soils lose about 15 to 40 Mg C ha 1 of their original C pool and can sequester 60 to 70 percent of the depleted C pool with the adoption species capable to produce high biomass. Improvement in soil quality under bioenergy crops depends on species capable of high productivity, fertilization, and harvest management. Figure 6: Carbon partitioning and translocations in bioenergy crop production system 11

12 References 1. Ausilio Bauen; Göran Berndes, Martin Junginger; Marc Londo and François Vuille Bioenergy A Sustainable and reliable energy source, a review of status and prospects Lead authors: Bransby, D. I., McLaughlin, S. B., and Parrish, D. J Soil carbon changes and nutrient cycling associated with switchgrass. Biomass and Bioenergy 14: Corre, M. D., Schnabel, R. R., and Shaffer, J. A Evaluation of soil organic carbon under forests, cool-season, and warm-season grasses in the northeastern U.S. Soil Biol. Biochem. 31: nline.pdf guidelines-english.pdf 8. rt4_v4_418.pdf 9. nts_soil_air_water.pdf John Wiley & Sons Ltd,, A reassessment of global bioenergy potential in 2050, GCB Bioenergy, 7, , Kort, J., Collins, M., and Ditsch, D A review of soil erosion potential associated with biomass crops. Biomass and Bioenergy 14(4): Lal, R Soil carbon dynamics in crop and rangeland. Environ. Pollut. 116: Potter, K. N., Tobert, H. A., Johnson, H. B., and Tischler, C. R Carbon storage after long-term grass establishment on degraded soils. Soil Sci. 164: R. Lemus and R. Lal, Bioenergy Crops and Carbon Sequestration Critical Reviews in Plant Sciences, 24:1 21, Study on Impacts on Resource Efficiency of Future EU Demand for Bioenergy, 2016, task2: sk%202.pdf. 18. Study on Impacts on Resource Efficiency of Future EU Demand for Bioenergy, 2016, task2: sk%202.pdf 12