The current use of agro biomass for energy generation is low and more efficient use would release significant amounts of agro biomass resources for other energy use. Usually, efficiency improvements are neglected because of the non-existence of grid connections with agro-industries.
Electricity generated from biomass is more costly to produce than fossil fuel and hydroelectric power for two reasons. First, biomass fuels are expensive. The cost of producing biomass fuel is dependent on the type of biomass, the amount of processing necessary to convert it to an efficient fuel, distance to the energy conversion plant, and supply and demand for fuels in the market place. Biomass fuel is low-density and non-homogeneous and has a small unit size.
Consequently, biomass fuel is costly to collect, process, and transport to facilities. Second, biomass-to-energy facilities are much smaller than conventional fossil fuel-based power plants and therefore cannot produce electricity as cost-effectively as the fossil fuel-based plants.
Agro biomass is costly to collect, process, and transport to facilities.
The biomass-to-energy facilities are smaller because of the limited amount of fuel that can be stored at a single facility. With higher fuel costs and lower economic efficiencies, solid-fuel energy is not economically competitive in a deregulated energy market that gives zero value or compensation for the non-electric benefits generated by the biomass-to-energy industry.
Biomass availability for fuel usage is estimated as the total amount of plant residue remaining after harvest, minus the amount of plant material that must be left on the field for maintaining sufficient levels of organic matter in the soil and for preventing soil erosion. While there are no generally agreed-upon standards for maximum removal rates, a portion of the biomass material may be removed without severely reducing soil productivity.
Technically, biomass removal rates of up to 60 to 70 percent are achievable, but in practice, current residue collection techniques generally result in relatively low recovery rates in developing countries. The low biomass recovery rate is the result of a combination of factors, including collection equipment limitations, economics, and conservation requirements. Modern agricultural equipment can allow for the joint collection of grain and residues, increased collection rates to up to 60 percent, and may help reduce concerns about soil compaction.
Sugarcane trash (or cane trash) is an excellent biomass resource in sugar-producing countries worldwide. The amount of cane trash produced depends on the plant variety, age of the crop at harvest and soil and weather conditions. Typically it represents about 15% of the total above ground biomass at harvest which is equivalent to about 10-15 tons per hectare of dry matter. During the harvesting operation around 70-80% of the cane trash is left in the field with 20-30% taken to the mill together with the sugarcane stalks as extraneous matter.
Cane trash’s calorific value is similar to that of bagasse but has an advantage of having lower moisture content, and hence dries more quickly. Nowadays only a small quantity of this biomass is used as fuel, mixed with bagasse or by itself, at the sugar mill. The rest is burned in the vicinity of the dry cleaning installation, creating a pollution problem in sugar-producing nations.
Cane trash and bagasse are produced during the harvesting and milling process of sugarcane which normally lasts between 6 to 7 months. Cane trash can potentially be converted into heat and electrical energy. However, most of the trash is burned in the field due to its bulky nature and high cost incurred in collection and transportation.
Cane trash could be used as an off-season fuel for year-round power generation at sugar mills. There is also a high demand for biomass as a boiler fuel during the sugar-milling season. Sugarcane trash can also converted in biomass pellets and used in dedicated biomass power stations or co-fired with coal in power plants and cement kilns.
Burning of cane trash creates pollution in sugar-producing countries
Currently, a significant percentage of energy used for boilers in sugarcane processing is provided by imported bunker oil. Overall, the economic, environmental, and social implications of utilizing cane trash in the final crop year as a substitute for bunker oil appears promising. It represents an opportunity for developing biomass energy use in the Sugarcane industry as well as for industries / communities in the vicinity.
Positive socio-economic impacts include the provision of large-scale rural employment and the minimization of oil imports. It can also develop the expertise necessary to create a reliable biomass supply for year-round power generation.
Recovery of Cane Trash
Recovery of cane trash implies a change from traditional harvesting methods; which normally consists of destroying the trash by setting huge areas of sugarcane fields ablaze prior to the harvest. There are a number of major technical and economic issues that need to be overcome to utilize cane trash as a renewable energy resource. For example, its recovery from the field and transportation to the mill, are major issues.
Alternatives include the current situation where the cane is separated from the trash by the harvester and the two are transported to the mill separately, to the harvesting of the whole crop with separation of the cane and the trash carried out at the mill. Where the trash is collected from the field it maybe baled incurring a range of costs associated with bale handling, transportation and storage. Baling also leaves about 10-20% (1-2 tons per hectare) of the recoverable trash in the field.
A second alternative is for the cane trash to be shredded and collected separately from the cane during the harvesting process. The development of such a harvester-mounted cane trash shredder and collection system has been achieved but the economics of this approach require evaluation. A third alternative is to harvest the sugarcane crop completely which would require an adequate collection, transport and storage system in addition to a mill based cleaning plant to separate the cane from the trash .
A widespread method for cane trash recovery is to cut the cane, chop into pieces and then it is blown in two stages in the harvester to remove the trash. The amount of trash that goes along with the cane is a function of the cleaning efficiency of the harvester. The blowers are adjusted to get adequate cleaning with a bearable cane loss.
On the average 68 % of the trash is blown out of the harvester, and stays on the ground, and 32 % is taken to the mill together with the cane as extraneous matter. The technique used to recover the trash staying on the ground is baling. Several baling machines have been tested with small, large, round and square bales. Cane trash can be considered as a viable fuel supplementary to bagasse to permit year-round power generation in sugar mills.
Thus, recovery of cane trash in developing nations of Asia, Africa and Latin America implies a change from traditional harvesting methods, which normally consists of destroying the trash by setting huge areas of cane fields ablaze prior to the harvest. To recover the trash, a new so-called “green mechanical harvesting” scheme will have to be introduced. By recovering the trash in this manner, the production of local air pollutants, as well as greenhouse gases contributing to adverse climatic change, from the fires are avoided and cane trash could be used as a means of regional sustainable development.
Cane Trash Recovery in Cuba
The sugarcane harvesting system in Cuba is unique among cane-producing countries in two important respects. First, an estimated 70 % of the sugarcane crop is harvested by machine without prior burning, which is far higher than for any other country. The second unique feature of Cuban harvesting practice is the long-standing commercial use of “dry cleaning stations” to remove trash from the cane stalks before the stalks are transported to the crushing mills.
Cuba has over 900 cleaning stations to serve its 156 sugar mills. The cleaning stations are generally not adjacent to the mills, but are connected to mills by a low-cost cane delivery system – a dedicated rail network with more than 7000 km of track. The cleaning stations take in green machine-cut or manually cut cane. Trash is removed from the stalk and blown out into a storage area. The stalks travel along a conveyor to waiting rail cars. The predominant practice today is to incinerate the trash at the cleaning station to reduce the “waste” volume.
Biomass exchange is emerging as a key factor in the progress of biomass energy sector. It is well-known that the supply chain management in any biomass project is a big management conundrum. The complexity deepens owing to the large number of stages which encompass the entire biomass value chain. It starts right from biomass resource harvesting and goes on to include biomass collection, processing, storage and eventually its transportation to the point of ultimate utilization.
Owing to the voluminous nature of the resource, its handling becomes a major issue since it requires bigger modes of biomass logistics, employment of a larger number of work-force and a better storage infrastructure, as compared to any other fuel or feedstock. Not only this their lower energy density characteristic, makes it inevitable for the resource to be first processed and then utilized for power generation to make for better economics.
All these problems call for a mechanism to strengthen the biomass value chain. This can be done by considering the following:
Assuring a readily available market for the resource providers or the producers
Assuring the project developers of a reliable chain and consistent feedstock availability
Awareness to the project developer of the resources in closest proximity to the plant site
Assurance to the project developer of the resource quality
Timely pick-up and drop of resource
Proper fuel preparation as per technology requirements
Removal of intermediaries involved in the process – to increase value for both, the producers as well as the buyers
No need for long term contracts (Not an obligation)
Competitive fuel prices
Assistance to producers in crop management
Biomass Exchange Model
The figure below gives a general understanding of how such a model could work, especially in the context of developing nations where the size of land holdings is usually small and the location of resources is scattered, making their procurement a highly uneconomic affair. This model is commonly known as Biomass Exchange
In such a model, the seed, fertilizer shops and other local village level commercial enterprises could be utilized as an outreach or marketing platform for such a service. Once the producer approves off the initial price estimate, as provided by these agencies, he could send a sample of the feedstock to the pre-deputed warehouses for a quality check.
These warehouses need to be organized at different levels according to the village hierarchy and depending on the size, cultivated area and local logistic options available in that region. On assessing the feedstock sample’s quality, these centers would release a plausible quote to the farmer after approving which, he would be asked to supply the feedstock.
On the other hand, an entity in need of the feedstock would approach the biomass exchange, where it would be appraised of the feedstock available in the region near its utilization point and made aware of the quantity and quality of the feedstock. The entity would then quote a price according to its suitability which would be relayed to the primary producer.
An agreement from both the sides would entail the placement of order and the feedstock’s subsequent processing and transportation to the buyer’s gate. The pricing mechanisms could be numerous ranging from, fixed (according to quality), bid-based or even market-driven.
The hurdles could be in the form of the initial resource assessment which could in itself be a tedious and time consuming exercise. Another roadblock could be in the form of engaging the resource producers with such a mechanism. Since these would usually involve rural landscapes, things could prove to be a little difficult in terms of implementation of initial capacity building measures and concept marketing.
The benefits of a biomass exchange are enumerated below:
Support to the ever increasing power needs of the country
Promotion of biomass energy technologies
Development of rural infrastructure
Increased opportunities for social and micro-entrepreneurship
Creation of direct and indirect job opportunities
Efficient utilization of biomass wastes
Potential of averting millions of tonnes of GHGs emissions
In India alone, there has been several cases where biomass power projects of the scale greater than 5 MW are on sale already, even with their power purchase agreements still in place. Such events necessitate the need to have a mechanism in place which would further seek the promotion of such technologies.
Biomass Exchange is an attractive solution to different problems afflicting biomass projects, at the same time providing the investors and entrepreneurs with a multi-million dollar opportunity. Although such a concept has been in existence in the developed world for a long time now, it has not witnessed many entrepreneurial ventures in developing nations where the need to strengthen the biomass supply chain becomes even more necessary.
However, one needs to be really careful while initiating such a model since it cannot be blindly copied from Western countries owing to entirely different land-ownership patterns, regional socio-political conditions and economic framework. With a strong backup and government support, such an idea could go a long way in strengthening the biomass supply chain, promotion of associated clean energy technologies and in making a significant dent in the present power scenario in the developing world.
Biomass is one of the oldest and simplest ways of getting heat and energy, and it’s starting to make a comeback due to its status as renewable resource. Some, however, aren’t so sure that using more of it would be good for our environment. So, how sustainable is biomass energy really?
What is Biomass?
Biomass is organic material from plants and animals. It naturally contains energy because plants absorb it from the sun through photosynthesis. When you burn biomass, it releases that energy. It’s also sometimes converted into a liquid or gas form before it is burned.
Biomass includes a wide variety of materials but includes:
About five percent of the United States’ energy comes from biomass. Biomass fuel products such as ethanol make up about 48 percent of that five percent while wood makes up about 41 percent and municipal waste accounts for around 11 percent.
The Benefits of Biomass
Biomass is a renewable resource because the plants that store the energy released when it is burned can be regrown continuously. In theory, if you planted the same amount of vegetation that you burned, it would be carbon neutral because the plants would absorb all of the carbon released. Doing this is, however, much easier said than done.
Another potential is that it serves as a use for waste materials that have are already been created. It adds value to what otherwise would be purely waste.
While you can replenish the organic matter you burn, doing so requires complex crop or forest management and the use of a large amount of land. Also, some biomass, such as wood, takes a long time to grow back. This amounts to a delay in carbon absorption. Additionally, the harvesting of biomass will likely involve some sort of emissions.
Is it Sustainable?
So, is biomass energy sustainable? Measuring the environmental impacts of biomass fuel use has proven to be complex due to the high number of variables, which has led to a lot of disagreement about this question.
Some assert that biomass use cannot be carbon neutral, because even if you burned and planted the same amount of organic matter, harvesting it would still result in some emissions. This could perhaps be avoided if you used renewable energy to harvest it. A continuous supply of biomass would likely require it to be transported long distances, worsening the challenge of going carbon neutral.
With careful planning, responsible land management and environmentally friendly harvesting and distribution, biomass could be close to, if not entirely, carbon neutral and sustainable. Given our reliance on fossil fuels, high energy consumption levels and the limited availability of land and other resources, this would be an immense challenge to undertake and require a complete overhaul of our energy use.
Source locally: Using biomass that comes from the local area reduces the impact of distributing it.
Clean distribution: If you do transport biofuel long distances, using an electric or hybrid vehicles powered largely by clean energy would be the most eco-friendly way to do it. This also applies to transporting it short distances.
Measuring the environmental impacts of biomass fuel use is complex due to high number of variables
Clean harvesting: Using environmentally friendly, non-emitting means of harvesting can greatly reduce the impact of using biomass. This might also involve electric vehicles.
Focus on waste: Waste is likely the most environmentally friendly form of biomass because it uses materials that would otherwise simply decompose and doesn’t require you to grow any new resources for your fuel or energy needs.
Is biomass energy sustainable? It has the potential to be, but doing so would be quite complex and require quite a bit of resources. Any easier way to address the problem is to look at small areas of land and portions of energy use first. First, make that sustainable and then we may be able to expand that model on to a broader scale.
Biomass energy systems offer significant possibilities for reducing greenhouse gas emissions due to their immense potential to replace fossil fuels in energy production. Biomass reduces emissions and enhances carbon sequestration since short-rotation crops or forests established on abandoned agricultural land accumulate carbon in the soil. Biomass energy usually provides an irreversible mitigation effect by reducing carbon dioxide at source, but it may emit more carbon per unit of energy than fossil fuels unless biomass fuels are produced in a sustainable manner.
Biomass resources can play a major role in reducing the reliance on fossil fuels by making use of thermo-chemical conversion technologies. In addition, the increased utilization of biomass-based fuels will be instrumental in safeguarding the environment, generation of new job opportunities, sustainable development and health improvements in rural areas.
The development of efficient biomass handling technology, improvement of agro-forestry systems and establishment of small and large-scale biomass-based power plants can play a major role in sustainable development of rural as well as urban areas. Biomass energy could also aid in modernizing the agricultural economy and creating significant job opportunities.
Harvesting practices remove only a small portion of branches and tops leaving sufficient biomass to conserve organic matter and nutrients. Moreover, the ash obtained after combustion of biomass compensates for nutrient losses by fertilizing the soil periodically in natural forests as well as fields.
The impact of forest biomass utilization on the ecology and biodiversity has been found to be insignificant. Infact, forest residues are environmentally beneficial because of their potential to replace fossil fuels as an energy source.
A quick glance at popular biomass resources
Plantation of energy crops on abandoned agricultural land will lead to an increase in species diversity. The creation of structurally and species diverse forests helps in reducing the impacts of insects, diseases and weeds. Similarly the artificial creation of diversity is essential when genetically modified or genetically identical species are being planted.
Short-rotation crops give higher yields than forests so smaller tracts are needed to produce biomass which results in the reduction of area under intensive forest management. An intelligent approach in forest management will go a long way in the realization of sustainability goals.
Improvements in agricultural practices promises to increased biomass yields, reductions in cultivation costs, and improved environmental quality. Extensive research in the fields of plant genetics, analytical techniques, remote sensing and geographic information systems (GIS) will immensely help in increasing the energy potential of biomass feedstock.
A large amount of energy is expended in the cultivation and processing of crops like sugarcane, coconut, and rice which can met by utilizing energy-rich residues for electricity production. The integration of biomass-fueled gasifiers in coal-fired power stations would be advantageous in terms of improved flexibility in response to fluctuations in biomass availability and lower investment costs. The growth of the biomass energy industry can also be achieved by laying more stress on green power marketing.
Biomass logistics include all the unit operations necessary to move biomass feedstock from the land to the biomass energy plant and to ensure that the delivered feedstock meets the specifications of the conversion process. The packaged biomass can be transported directly from farm or from stacks next to the farm to the processing plant.
Biomass may be minimally processed (i.e. ground) before being shipped to the plant, as in case of biomass supply from the stacks. Generally the biomass is trucked directly from farm to biorefinery if no processing is involved.
Another option is to transfer the biomass to a central location where the material is accumulated and subsequently dispatched to the energy conversion facility. While in depot, the biomass could be pre-processed minimally (ground) or extensively (pelletized). The depot also provides an opportunity to interface with rail transport if that is an available option.
The choice of any of the options depends on the economics and cultural practices. For example in irrigated areas, there is always space on the farm (corner of the land) where quantities of biomass can be stacked. The key components to reduce costs in harvesting, collecting and transportation of biomass can be summarized as:
Reduce the number of passes through the field by amalgamating collection operations.
Increase the bulk density of biomass
Work with minimal moisture content.
Granulation/pelletization is the best option, though the existing technology is expensive.
Trucking seems to be the most common mode of biomass transportation option but rail and pipeline may become attractive once the capital costs for these transport modes are reduced.
The logistics of transporting, handling and storing the bulky and variable biomass material for delivery to the bioenergy processing plant is a key part of the supply chain that is often overlooked by project developers. Whether the biomass comes from forest residues on hill country, straw residues from cereal crops grown on arable land, or the non-edible components of small scale, subsistence farming systems, the relative cost of collection will be considerable.
Careful development of a system to minimize machinery use, human effort and energy inputs can have a considerable impact on the cost of the biomass as delivered to the processing plant gate.
The logistics of supplying a biomass power plant with sufficient volumes of biomass from a number of sources at suitable quality specifications and possibly all year round, are complex. Agricultural residues can be stored on the farm until needed. Then they can be collected and delivered directly to the conversion plant on demand. Infact, this requires considerable logistics to ensure only a few days of supply are available on-site but that the risk of non-supply at any time is low.
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