Fuel Crop Miscanthus As A Green Energy Alternative: Today’s Resource For Future Environment





Science, 25 Oct - 2017 ,

Fuel Crop Miscanthus As A Green Energy Alternative: Today’s Resource For Future Environment
Credit: pixabay.com

Renewable energy source has been an alternative to non-renewable sources because of its non exhaustible nature, environmental security, and clean energy font for our future generation, job and economic stability

Renewable energy source has been an alternative to non-renewable sources because of its non exhaustible nature, environmental security, and clean energy font for our future generation, job and economic stability to the society. Biofuel (as a alternative to the gasoline and petroleum derived sources) and bioenergy (renewable) are the two important green energy alternative that can be obtained from biological sources like biomass and has got attention in the modern world due to its ecofriendly and ecostasis nature. Among various crops used for green energy, Miscanthus is one of the best alternative, high yielding large perennial energy crop which can produce lot of biomass. Miscanthus giganteus, has been trialled as a biofuel in Europe since the early 1980s. The rapid growth, low mineral absorption efficiency, environmental friendliness, low maintenance,  annual growing cycle, no use of fertilizer and pesticide, long life span, nutrient cycling ability and high biomass yield make it a favourite choice as a biofuel and bioenergy sources.

Miscanthus is a genus of abo0ut 15 species of perennial grasses native to subtropical and tropical regions of Africa and southern Asia, with one species (M. sinensis) extending north into temperate eastern Asia and sometimes called "elephant grass". It can grow to heights of more than 3.5 m in one growth season. Its dry weight annual yield can reach 25 tonnes per hectare (10 tonnes per acre). It has been trialled as a biofuel source in Europe since the early 1980s (http://www.biomassenergycentre.org.uk)

The major three products are a) miscanthus cane for bioethanol, high quality paper pulp through to plastic composites and luxury equine bedding, b) fuel pellets - Used in dedicated heating boilers and c) fuel briquettes- Due to long lifespan it can be used for wood burners, open fires and chimneys.

Scientific facts about Miscanthus

*      1 tonne of Miscanthus can produce 4 MW hours of heat the equivalent of 500 litres of heating oil.

*      1 tonne of \Miscanthus can produce 240 litres of biodiesel and based on 25 miles to the gallon, 1 tonne of Miscanthus could produce fuel to drive over 750 miles.

*      Every tonne of Miscanthus that replaces coal, prevents upto 2 tonnes of CO2being emitted.

*      The density of chipped Miscanthus is 60-80 kg/m3.

*      The density of plant biomass pellets is around 600kg/m³

*      1 tonne of Miscanthus could produce 1.8 MW of Electricity, the equivalent of 0.7t of coal and it is a carbon neutral, sustainable energy source, one that grows back every year.

*      The density of biomass energy cubes is approximately 450 -500kg/m³

*      Yield estimates 10-15 tons per acre

*      Excellent for carbon sequestration and soil building

Model proposed for conversion of biomass to electricity by use of briquettes

Making of biomass briquettes:

Briquetting presses may be of screw or piston type. In the first case, the biomass is screwed forward under high pressure through a nozzle (funnel shaped) in which case, the briquettes get its cylindrical shape. In the second case, the same forward pressure is effected with a piston. There are two methods to retain their cylindrical form. One of them operates with binding agent and the other without binding agent. Briquetting without binding agent requires a raw material with a maximum moisture content of 15 percent and a briquetting press which can generate a pressure of at least 1000 kg/cm2. The minimum pressure can vary depending upon the nature of raw material pressed. Briquetting with binding material does not require the same low moisture content which varies de- pending upon the-raw material. The four chief parameters of the briquetting process are: moisture, particle size, binding agent, and level of pressure. 

Miscanthus cane: Increasing use of gasoline based fuel has lead to serious consequences to the society. So there is a need of a swift alternative to this problem (Zaldivar et al., 2001). Biomass based production of ethanol (mostly cellulose) is the most promising technology for reducing emission of green house gases from transportation sector (Hahn-Hagerdal, 2006). Lignocellulosic material is widely available and requires pre-treatment to partially digest the complex sugars (in below table) to form simple sugars for fermentation by specific microorganisms. Acid and alkali treatment of the biomass tends to expose the lignocelluloses for enzymatic treatment to fragment it to xylose, glucose, galactose and other sugar alcohols. The most interesting fact about the Miscanthus is its efficient use of CO2 as it belongs to C4 plant family and hence reduced rate of photorespiration. So over all it is the best user of CO2 and hence plays key role in CO2 sequestration. The hydrolysed fermentable sugars are used for fermentation by utilizing yeast (Saccharomyces cerevisiae strains) and molds (Aspergillus sp.) to produce ethanol as a fermentation product.

Table 1: Major components of Miscanthus from Han et al., 2011

Components

Percentage (%)

Cellulose

37.00

Hemi-cellulose

22.12

Acid insoluble lignin

20.43

Acid soluble lignin

2.88

Moisture

7.02

Ash

2.84

Conclusion

Lignocellulosic biomass as the widely available and cost effective and is considered to be the most effective source for bioethanol production. The preliminary step of exposure of poly sugar moiety to enzymatic hydrolysis is the critical for production context. So many of the methods have been tried by researchers and currently people are focusing on non-chemical and natural method (biological method) using white/brown/soft rot fungi are the preferable organisms for pre treatment as well as enzymatic hydrolysis. Extensive research is still going on to increase fermentable carbohydrate recovery from sugar degradation during pretreatment and decrease cost of bioethanol process. Combination of more than one method is the best for maximum bioethanol production from biomass sources. Miscanthus giganteus is the best alternative for such cost effective and environmental friendly way of biofuel production. Recent advances in genomics and genetic engineering imply that bioethanol production from biomass will be the foremost technique for replacing gasoline and petroleum based fuel as sustainable, clean and green energy source for near tomorrow. 


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