Ethanol from Lignocellulosic Biomass

Cellulosic ethanol technology is one of the most commonly discussed second-generation biofuel technologies worldwide. Cellulosic biofuels are derived from the cellulose in plants, some of which are being developed specifically as “energy” crops rather than for food production. These include perennial grasses and trees, such as switchgrass and Miscanthus. Crop residues, in the form of stems and leaves, represent another substantial source of cellulosic biomass.

The largest potential feedstock for ethanol is lignocellulosic biomass, which includes materials such as agricultural residues (corn stover, crop straws, husks and bagasse), herbaceous crops (alfalfa, switchgrass), short rotation woody crops, forestry residues, waste paper and other wastes (municipal and industrial). Bioethanol production from these feedstocks could be an attractive alternative for disposal of these residues. Lignocellulosic feedstocks do not interfere with food security and are important for both rural and urban areas in terms of energy security reason, environmental concern, employment opportunities, agricultural development, foreign exchange saving, socioeconomic issues etc.

Production of Ethanol

The production of ethanol from lignocellulosic biomass can be achieved through two different processing routes. They are:

  • Biochemical – in which enzymes and other micro-organisms are used to convert cellulose and hemicellulose components of the feedstocks to sugars prior to their fermentation to produce ethanol;
  • Thermochemical – where pyrolysis/gasification technologies produce a synthesis gas (CO + H2) from which a wide range of long carbon chain biofuels, such as synthetic diesel or aviation fuel, can be reformed.

Lignocellulosic biomass consists mainly of lignin and the polysaccharides cellulose and hemicellulose. Compared with the production of ethanol from first-generation feedstocks, the use of lignocellulosic biomass is more complicated because the polysaccharides are more stable and the pentose sugars are not readily fermentable by Saccharomyces cerevisiae. In order to convert lignocellulosic biomass to biofuels the polysaccharides must first be hydrolysed, or broken down, into simple sugars using either acid or enzymes. Several biotechnology-based approaches are being used to overcome such problems, including the development of strains of Saccharomyces cerevisiae that can ferment pentose sugars, the use of alternative yeast species that naturally ferment pentose sugars, and the engineering of enzymes that are able to break down cellulose and hemicellulose into simple sugars.

Ethanol from lignocellulosic biomass is produced mainly via biochemical routes. The three major steps involved are pretreatment, enzymatic hydrolysis, and fermentation. Biomass is pretreated to improve the accessibility of enzymes. After pretreatment, biomass undergoes enzymatic hydrolysis for conversion of polysaccharides into monomer sugars, such as glucose and xylose. Subsequently, sugars are fermented to ethanol by the use of different microorganisms.

Pretreated biomass can directly be converted to ethanol by using the process called simultaneous saccharification and cofermentation (SSCF).  Pretreatment is a critical step which enhances the enzymatic hydrolysis of biomass. Basically, it alters the physical and chemical properties of biomass and improves the enzyme access and effectiveness which may also lead to a change in crystallinity and degree of polymerization of cellulose. The internal surface area and pore volume of pretreated biomass are increased which facilitates substantial improvement in accessibility of enzymes. The process also helps in enhancing the rate and yield of monomeric sugars during enzymatic hydrolysis steps.

Pretreatment of Lignocellulosic Biomass

Pretreatment methods can be broadly classified into four groups – physical, chemical, physio-chemical and biological. Physical pretreatment processes employ the mechanical comminution or irradiation processes to change only the physical characteristics of biomass. The physio-chemical process utilizes steam or steam and gases, like SO2 and CO2. The chemical processes employs acids (H2SO4, HCl, organic acids etc) or alkalis (NaOH, Na2CO3, Ca(OH)2, NH3 etc). The acid treatment typically shows the selectivity towards hydrolyzing the hemicelluloses components, whereas alkalis have better selectivity for the lignin. The fractionation of biomass components after such processes help in improving the enzymes accessibility which is also important to the efficient utilization of enzymes.

Conclusions

The major cost components in bioethanol production from lignocellulosic biomass are the pretreatment and the enzymatic hydrolysis steps. In fact, these two process are someway interrelated too where an efficient pretreatment strategy can save substantial enzyme consumption. Pretreatment step can also affect the cost of other operations such as size reduction prior to pretreatment. Therefore, optimization of these two important steps, which collectively contributes about 70% of the total processing cost, are the major challenges in the commercialization of bioethanol from 2nd generation feedstock.

Biomass Resources in Malaysia

Malaysia is gifted with conventional energy resources such as oil and gas as well as renewables like hydro, biomass and solar energy. As far as biomass resources in Malaysia are concerned, Malaysia has tremendous agricultural biomass and wood waste resources available for immediate exploitation. This energy potential of biomass resource is yet to be exploited properly in the country.

Taking into account the growing energy consumption and domestic energy supply constraints, Malaysia has set sustainable development and diversification of energy sources, as the economy’s main energy policy goals. The Five-Fuel Strategy recognises renewable energy resources as the economy’s fifth fuel after oil, coal, natural gas and hydro. Being a major agricultural commodity producer in the region Malaysia is well positioned amongst the ASEAN countries to promote the use of biomass as a source of renewable energy.

Major Biomass Resources

Palm Oil Biomass

Malaysia is the world’s leading exporter of palm oil, exporting more than 19.9 million tonnes of palm oil in 2017. The extraction of palm oil from palm fruits results in a large quantity of waste in the form of palm kernel shells, empty fruit bunches and mesocarp fibres. In 2011, more than 80 million tons of oil palm biomass was generated across the country.

13MW biomass power plant at a palm oil mill in Sandakan, Sabah (Malaysia)

Processing crude palm oil generates a foul-smelling effluent, called Palm Oil Mill Effluent or POME, which when treated using anaerobic processes, releases biogas. Around 58 million tons of POME is produced in Malaysia annually, which has the potential to produce an estimated 15 billion m3 of biogas.

Rice Husk

Rice husk is another important agricultural biomass resource in Malaysia with very good energy potential for biomass cogeneration. An example of its attractive energy potential is biomass power plant in the state of Perlis which uses rice husk as the main source of fuel and generates 10 MW power to meet the requirements of 30,000 households.

Municipal Solid Wastes

The per capita generation of solid waste in Malaysia varies from 0.45 to 1.44kg/day depending on the economic status of an area. Malaysian solid wastes contain very high organic waste and consequently high moisture content and bulk density of above 200kg/m3. The high rate of population growth is the country has resulted in rapid increase in solid waste generation which is usually dumped in landfills.

Conclusion

Biomass resources have long been identified as sustainable source of renewable energy particularly in countries where there is abundant agricultural activities. Intensive use of biomass as renewable energy source in Malaysia could reduce dependency on fossil fuels and significant advantage lies in reduction of net carbon dioxide emissions to atmosphere leading to less greenhouse effect. However, increased competitiveness will require large-scale investment and advances in technologies for converting this biomass to energy efficiently and economically.

The Role of Biofuel in Low-Carbon Transport

Biofuels offer a solution to climate change that shouldn’t go ignored. In fact, the amount of biofuel used in transport has to increase by a factor of seven in order to prevent climate catastrophe, a recent report on 1.5C warming by the Intergovernmental Panel on Climate Change (IPCC) states. The report also places biofuels in the same league of importance as electric vehicles when it comes to replacing unsustainable fossil fuels by 2050.

Biofuels are increasingly being used to power vehicles around the world

Electric cars: benefits and limitations

A typical gas-powered car emits roughly one pound of carbon dioxide per mile traveled. On the other hand, electric cars release zero tailpipe emissions. However, light-duty passenger vehicles represent only 50% of the energy demand in the transportation sector worldwide.

Heavy road vehicles and air, sea, and rail transport make up the rest — electrification of this remaining 50% would be an expensive task. Additionally, demand for transport is expected to increase in the future. Vehicles will need to use even less energy by 2050 to ensure the global transport sector’s total energy demand rises no higher than current levels (100 exajoules).

Biofuel: a necessary solution

Several sustainable, carbon-neutral synthetic fuels are currently in developmental and demonstration stages. For example, synfuels can be produced from carbon dioxide and water via low-carbon electricity. However, this also requires cheap and low-carbon power systems (similar to the ones already running in Quebec and Iceland).

Biodiesel

In 2013, Audi was the first automaker to establish an electrofuel plant — it cost €20M and produces 3.2 MW of synthetic methane from 6 MW of electricity. Additionally, synthetic biofuels can be made from woody residues and crop wastes, which has a lighter environmental footprint than biofuels made from agricultural crops.

Examples of eco-friendly cars

While biofuels continue to be developed, there are plenty of electric cars on the market right now — all of which can help us reduce our individual carbon footprints. For example, the Hyundai Kona Electric is an impressive electric car. This vehicle offers sleek exterior styling, plenty of modern tech features, and has an impressive range of 258 miles in between charges. The price starts at $36,950. Alternatively, the Nissan LEAF is another eco-friendly model priced from $29,990. It’s powered by an 80kW electric motor and runs for 100 miles per charge.

Electric cars and synthetic biofuels are both valuable technological changes. Focusing on developing both of these sustainable options should take utmost priority in the fight against climate change.

Biomass Energy Scenario in Southeast Asia

The rapid economic growth and industrialization in Southeast Asian region is characterized by a significant gap between energy supply and demand. The energy demand in the region is expected to grow rapidly in the coming years which will have a profound impact on the global energy market. In addition, the region has many locations with high population density, which makes public health vulnerable to the pollution caused by fossil fuels.

Another important rationale for transition from fossil-fuel-based energy systems to renewable ones arises out of observed and projected impacts of climate change. Due to the rising share of greenhouse gas emissions from Asia, it is imperative on all Asian countries to promote sustainable energy to significantly reduce GHGs emissions and foster sustainable energy trends. Rising proportion of greenhouse gas emissions is causing large-scale ecological degradation, particularly in coastal and forest ecosystems, which may further deteriorate environmental sustainability in the region.

The reliance on conventional energy sources can be substantially reduced as the Southeast Asian region is one of the leading producers of biomass resources in the world. Southeast Asia, with its abundant biomass resources, holds a strategic position in the global biomass energy atlas.

There is immense potential of biomass energy in ASEAN countries due to plentiful supply of diverse forms of wastes such as agricultural residues, agro-industrial wastes, woody biomass, animal wastes, municipal solid waste, etc. Southeast Asia is a big producer of wood and agricultural products which, when processed in industries, produces large amounts of biomass residues.

palm-kernel-shell-uses

Palm kernel shells is an abundant biomass resource in Southeast Asia

According to conservative estimates, the amount of biomass residues generated from sugar, rice and palm oil mills is more than 200-230 million tons per year which corresponds to cogeneration potential of 16-19 GW. Woody biomass is a good energy resource due to presence of large number of forests and wood processing industries in the region.

The prospects of biogas power generation are also high in the region due to the presence of well-established food processing, agricultural and dairy industries. Another important biomass resource is contributed by municipal solid wastes in heavily populated urban areas.

In addition, there are increasing efforts from the public and private sectors to develop biomass energy systems for efficient biofuel production, e.g. biodiesel and bioethanol. The rapid economic growth and industrialization in Southeast Asia has accelerated the drive to implement the latest biomass energy technologies in order to tap the unharnessed potential of biomass resources, thereby making a significant contribution to the regional energy mix.

Biodiesel Program in India – An Analysis

The Government of India approved the National Policy on Biofuels in December 2009. The biofuel policy encouraged the use of renewable energy resources as alternate fuels to supplement transport fuels (petrol and diesel for vehicles) and proposed a target of 20 percent biofuel blending (both biodiesel and bioethanol) by 2017. The government launched the National Biodiesel Mission (NBM) identifying Jatropha curcas as the most suitable tree-borne oilseed for biodiesel production.

The Planning Commission of India had set an ambitious target covering 11.2 to 13.4 million hectares of land under Jatropha cultivation by the end of the 11th Five-Year Plan. The central government and several state governments are providing fiscal incentives for supporting plantations of Jatropha and other non-edible oilseeds. Several public institutions, state biofuel boards, state agricultural universities and cooperative sectors are also supporting the biofuel mission in different capacities.

State of the Affairs

The biodiesel industry in India is still in infancy despite the fact that demand for diesel is five times higher than that for petrol. The government’s ambitious plan of producing sufficient biodiesel to meet its mandate of 20 percent diesel blending by 2012 was not realized due to a lack of sufficient Jatropha seeds to produce biodiesel.

Currently, Jatropha occupies only around 0.5 million hectares of low-quality wastelands across the country, of which 65-70 percent are new plantations of less than three years. Several corporations, petroleum companies and private companies have entered into a memorandum of understanding with state governments to establish and promote Jatropha plantations on government-owned wastelands or contract farming with small and medium farmers. However, only a few states have been able to actively promote Jatropha plantations despite government incentives.

Key Hurdles

The unavailability of sufficient feedstock and lack of R&D to evolve high-yielding drought tolerant Jatropha seeds have been major stumbling blocks. In addition, smaller land holdings, ownership issues with government or community-owned wastelands, lackluster progress by state governments and negligible commercial production of biodiesel have hampered the efforts and investments made by both private and public sector companies.

The non-availability of sufficient feedstock and lack of R&D to evolve high-yielding drought tolerant Jatropha seeds have been major stumbling blocks in biodiesel program in India. In addition, smaller land holdings, ownership issues with government or community-owned wastelands, lackluster progress by state governments and negligible commercial production of biodiesel have hampered the efforts and investments made by both private and public sector companies.

Another major obstacle in implementing the biodiesel programme has been the difficulty in initiating large-scale cultivation of Jatropha. The Jatropha production program was started without any planned varietal improvement program, and use of low-yielding cultivars made things difficult for smallholders. The higher gestation period of biodiesel crops (3–5 years for Jatropha and 6–8 years for Pongamia) results in a longer payback period and creates additional problems for farmers where state support is not readily available.

The Jatropha seed distribution channels are currently underdeveloped as sufficient numbers of processing industries are not operating. There are no specific markets for Jatropha seed supply and hence the middlemen play a major role in taking the seeds to the processing centres and this inflates the marketing margin.

Biodiesel distribution channels are virtually non-existent as most of the biofuel produced is used either by the producing companies for self-use or by certain transport companies on a trial basis. Further, the cost of biodiesel depends substantially on the cost of seeds and the economy of scale at which the processing plant is operating.

The lack of assured supplies of feedstock supply has hampered efforts by the private sector to set up biodiesel plants in India. In the absence of seed collection and oil extraction infrastructure, it becomes difficult to persuade entrepreneurs to install trans-esterification plants.

Major Considerations in Biopower Projects

In recent years, biopower (or biomass power) projects are getting increasing traction worldwide, however there are major issues to be tackled before setting up a biopower project. There are three important steps involved in the conversion of biomass wastes into useful energy. In the first step, the biomass must be prepared for the energy conversion process. While this step is highly dependent on the waste stream and approach, drying, grinding, separating, and similar operations are common.

In addition, the host facility will need material handling systems, storage, metering, and prep-yard systems and biomass handling equipment. In the second step, the biomass waste stream must be converted into a useful fuel or steam. Finally, the fuel or steam is fed into a prime mover to generate useful electricity and heat.

One of the most important factors in the efficient utilization of biomass resource is its availability in close proximity to a biomass power project. An in-depth evaluation of the available quantity of a given agricultural resource should be conducted to determine initial feasibility of a project, as well as subsequent fuel availability issues. The primary reasons for failure of biomass power projects are changes in biomass fuel supply or demand and changes in fuel quality.

Fuel considerations that should be analyzed before embarking on a biomass power project include:

  • Typical moisture content (including the effects of storage options)
  • Typical yield
  • Seasonality of the resource
  • Proximity to the power generation site
  • Alternative uses of the resource that could affect future availability or price
  • Range of fuel quality
  • Weather-related issues
  • Percentage of farmers contracted to sell residues

Accuracy is of great importance in making fuel availability assumptions because miscalculations can greatly impact the successful operation of biomass power projects. If biomass resource is identifies as a bottle-neck in the planning stage, a power generation technology that can handle varying degrees of moisture content and particle size can be selected.

Technologies that can handle several fuels in a broad category, such as agricultural residues, provide security in operation without adversely affecting combustion efficiency, operations and maintenance costs, emissions levels, and reliability.

Consistent and reliable supply of biomass is crucial for any biomass project

Identification of potential sources of biomass fuel can be one of the more challenging aspects of a new biomass energy project. There are two important issues for potential biomass users:

  • Consistent and reliable biomass resource supply to the facility
  • Presence of harvesting, processing and supply infrastructure to provide biomass in a consistent and timely manner

Biomass as an energy source is a system of interdependent components. Economic and technical viability of this system relies on a guaranteed feedstock supply, effective and efficient conversion technologies, guaranteed markets for the energy products, and cost-effective distribution systems.

The biomass system is based on the following steps:

  • Biomass harvesting (or biomass collection of non-agricultural waste)
  • Preparation of biomass as feedstock
  • Conversion of biomass feedstock into intermediate products.
  • Transformation of intermediates into final energy and other bio-based products
  • Distribution and utilization of biofuels, biomass power and bio-based products.

Why Biofuels Should Be a Key Part in America’s Future

Biofuels are one of the hottest environmental topics, but they aren’t anything new. When discussing these fuels, experts frequently refer to first, second-and third-generation biofuels to differentiate between more efficient and advanced ones currently in development and more traditional biofuels in use for decades.

Biofuels are increasingly being used to power vehicles around the world

First-generation biofuels are things like methanol, ethanol, biodiesel and vegetable oil, while second-generation biofuels are produced by transforming crops into liquid fuels using highly advanced chemical processes, such as mixed alcohols and biohydrogen. Third-generation, or “advanced” biofuels, are created using oil that is made from algae or closed reactors and then refined to produce conventional fuels such as ethanol, methane, biodiesel, etc.

Cleaner Air and Less Impact on Climate Change

As biofuels come from renewable materials, they have less of an impact on climate change as compared to gasoline, according to multiple studies. Ethanol in gasoline has been helping to decrease smog in major cities, keeping the air cleaner and safer to breathe. Starch-based biofuels can reduce carbon dioxide emissions by around 30- to 60-percent, as compared to gasoline, while cellulosic ethanol can lessen emissions even further, as much as 90 percent.

Reduced Danger of Environmental Disaster

Can you imagine buying one of the oceanfront Jacksonville condos in Florida, looking forward to enjoying peaceful beach strolls every morning only to find injured or killed animals and globs of oil all over the sand? Not exactly the vision of paradise you dreamed of.

A major benefit of using biofuels is the risk of environmental disaster is dramatically reduced. The 2010 Deepwater Horizon Spill that occurred in the Gulf of Mexico released millions of gallons of oil. It not only cost BP nearly $62 billion but caused extensive damage to wildlife and the environment. Biofuels are much safer. For example, a corn field won’t poison the ocean.

More Jobs and an Economic Boom

Numerous studies, including one conducted by the Renewable Fuels Association (RFA), have found that biofuels lead to more jobs for Americans. In 2014, the ethanol industry was responsible for nearly 84,000 direct jobs and over 295,000 indirect and induced jobs – all jobs that pay well and are non-exportable. The industry also added nearly $53 billion to the national GDP, $27 billion to the national GDP and over $10 billion in taxes, stimulating local, state and national economies.

Many experts predict that these figures will increase with significant job creation potential in biorefinery construction, operation and biomass collection. If the potential for producing cellulosic ethanol from household waste and forestry residues were utilized at commercial scale, even more jobs are likely to be added.

Energy Independence

When a nation has the land resources to grow biofuel feedstock, it is able to produce its own energy, eliminating dependence on fossil fuel resources. Considering the significant amount of conflict that tends to happen over fuel prices and supplies, this brings a net positive effect.

Bioenergy Developments in Malaysia

Malaysia is blessed with abundant renewable sources of energy, especially biomass and solar. Under the Eighth Malaysian Plan, renewable energy was added in the energy mix to unveil a Five-Fuel Strategy to achieve 5 percent contribution by 2005.

Among the various sources of renewable energy, bioenergy seems to be the most promising option for Malaysia. The National Biofuel Policy, launched in 2006 encourages the use of environmentally friendly, sustainable and viable sources of biomass energy. Under the Five Fuel Policy, the government of Malaysia has identified biomass as one of the potential renewable energy. Malaysia produces atleast 168 million tonnes of biomass, including timber and oil palm waste, rice husks, coconut trunk fibres, municipal waste and sugar cane waste annually. Being a major agricultural commodity producer in the region Malaysia is well positioned amongst the ASEAN countries to promote the use of biomass as a renewable energy source.

Malaysia has been one of the world’s largest producers and exporters of palm oil for the last forty years. The Palm Oil industry, besides producing Crude Palm Oil (CPO) and Palm Kernel Oil, produces Palm Shell, Press Fibre, Empty Fruit Bunches (EFB), Palm Oil Mill Effluent (POME), Palm Trunk (during replanting) and Palm Fronds (during pruning).

Malaysia has approximately 4 million hectares of land under oil palm plantation. Over 75% of total area planted is located in just four states, Sabah, Johor, Pahang and Sarawak, each of which has over half a million hectares under cultivation. The total amount of processed FFB (Fresh Fruit Bunches) was estimated to be 75 million tons while the total amount of EFB produced was estimated to be 16.6 million tons. Around 58 million tons of POME is produced in Malaysia annually, which has the potential to produce an estimated 15 billion m3 of biogas can be produced each year.

Malaysia is the world’s second largest producer of crude palm oil. Almost 70% of the volume from the processing of fresh fruit bunch is removed as wastes in the form of empty fruit bunches, palm kernel shells, palm oil mill effluent etc. With more than 423 mills in Malaysia, this palm oil industry generated around 80 million dry tonnes of biomass in 2010. Malaysia has more than 2400 MW of biomass and 410 MW of biogas potential, out of which only 773MW has been harnessed until 2011.

Rice husk is another important agricultural biomass resource in Malaysia with good potential for power cogeneration. An example of its attractive energy potential is biomass power plant in the state of Perlis which uses rice husk as the main source of fuel and generates 10 MW power to meet the requirements of 30,000 households. The US$15 million project has been undertaken by Bio-Renewable Power Sdn Bhd in collaboration with the Perlis state government, while technology provider is Finland’s Foster Wheeler Energia Oy.

Under the EC-ASEAN Cogeneration Program, there are three ongoing Full Scale Demonstration Projects (FSDPs) – Titi Serong, Sungai Dingin Palm Oil Mill and TSH Bioenergy – to promote biomass energy systems in Malaysia. The 1.5MW Titi Serong power plant, located at Parit Buntar (Perak), is based on rice husk while the 2MW Sungai Dingin Palm Oil Mill project make use of palm kernel shell and fibre to generate steam and electricity. The 14MW TSH Bioenergy Sdn Bhd, located at Tawau (Sabah), is the biggest biomass power plant in Malaysia and utilizes empty fruit bunches, palm oil fibre and palm kernel shell as fuel resources.

Biofuels from Syngas

An attractive approach to converting biomass into liquid or gaseous fuels is direct gasification, followed by conversion of the gas to final fuel. Ethanol can be produced this way, but other fuels can be produced more easily and potentially at lower cost, though none of the approaches is currently inexpensive.

The choice of which process to use is influenced by the fact that lignin cannot easily be converted into a gas through biochemical conversion. Lignin can, however, be gasified through a heat process. The lignin components of plants can range from near 0% to 35%. For those plants at the lower end of this range, the chemical conversion approach is better suited. For plants that have more lignin, the heat-dominated approach is more effective.

Once the gasification of biomass is complete, the resulting gases can be used in a variety of ways to produce liquid fuels discussed, in brief, below

Fischer-Tropsch (F-T) fuels

The Fischer-Tropsch process converts “syngas” (mainly carbon monoxide and hydrogen) into diesel fuel and naphtha (basic gasoline) by building polymer chains out of these basic building blocks. Typically a variety of co-products (various chemicals) are also produced.  Figure 2.1 shows the production of diesel fuel from bio-syngas by Fisher-Tropsch synthesis (FTS).

The Fisher-Tropsch process is an established technology and has been proven on a large scale but adoption has been limited by high capital and O&M costs. According to Choren Industries, a German based developer of the technology, it takes 5 tons of biomass to produce 1 ton of biodiesel, and 1 hectare generates 4 tons of biodiesel.

Methanol

Syngas can also be converted into methanol through dehydration or other techniques, and in fact methanol is an intermediate product of the F-T process (and is therefore cheaper to produce than F-T gasoline and diesel). Methanol is somewhat out of favour as a transportation fuel due to its relatively low energy content and high toxicity, but might be a preferred fuel if fuel cell vehicles are developed with on-board reforming of hydrogen.

Dimethyl ether

DME also can be produced from syngas, in a manner similar to methanol. It is a promising fuel for diesel engines, due to its good combustion and emissions properties. However, like LPG, it requires special fuel handling and storage equipment and some modifications of diesel engines, and is still at an experimental phase. If diesel vehicles were designed and produced to run on DME, they would become inherently very low pollutant emitting vehicles; with DME produced from biomass, they would also become very low GHG vehicles.

Energy Potential of Bagasse

Sugarcane is one of the most promising agricultural sources of biomass energy in the world. Sugarcane produces mainly two types of biomass, Cane Trash and Bagasse. Cane Trash is the field residue remaining after harvesting the Cane stalk while bagasse is the fibrous residue left over after milling of the Cane, with 45-50% moisture content and consisting of a mixture of hard fibre, with soft and smooth parenchymatous (pith) tissue with high hygroscopic property. Bagasse contains mainly cellulose, hemi cellulose, pentosans, lignin, Sugars, wax, and minerals. The quantity obtained varies from 22 to 36% on Cane and is mainly due to the fibre portion in Cane and the cleanliness of Cane supplied, which, in turn, depends on harvesting practices.

The composition of Bagasse depends on the variety and maturity of Sugarcane as well as harvesting methods applied and efficiency of the Sugar processing. Bagasse is usually combusted in furnaces to produce steam for power generation. Bagasse is also emerging as an attractive feedstock for bioethanol production. It is also utilized as the raw material for production of paper and as feedstock for cattle. The value of Bagasse as a fuel depends largely on its calorific value, which in turn is affected by its composition, especially with respect to its water content and to the calorific value of the Sugarcane crop, which depends mainly on its sucrose content.

Moisture contents is the main determinant of calorific value i.e. the lower the moisture content, the higher the calorific value. A good milling process will result in low moisture of 45% whereas 52% moisture would indicate poor milling efficiency. Most mills produce Bagasse of 48% moisture content, and most boilers are designed to burn Bagasse at around 50% moisture. Bagasse also contains approximately equal proportion of fibre (cellulose), the components of which are carbon, hydrogen and oxygen, some sucrose (1-2 %), and ash originating from extraneous matter. Extraneous matter content is higher with mechanical harvesting and subsequently results in lower calorific value.

For every 100 tons of Sugarcane crushed, a Sugar factory produces nearly 30 tons of wet Bagasse. Bagasse is often used as a primary fuel source for Sugar mills; when burned in quantity, it produces sufficient heat and electrical energy to supply all the needs of a typical Sugar mill, with energy to spare. The resulting CO2 emissions are equal to the amount of CO2 that the Sugarcane plant absorbed from the atmosphere during its growing phase, which makes the process of cogeneration greenhouse gas-neutral.

35MW Bagasse and Coal CHP Plant in Mauritius

Cogeneration of Bagasse is one of the most attractive and successful energy projects that have already been demonstrated in many Sugarcane producing countries such as Mauritius, Reunion Island, India and Brazil. Combined heat and power from Sugarcane in the form of power generation offers renewable energy options that promote sustainable development, take advantage of domestic resources, increase profitability and competitiveness in the industry, and cost-effectively address climate mitigation and other environmental goals.