As the world population increases there is an increase in consumption and standard of living, eventually, energy demand also increases to fulfill it. The net energy demand cannot be satisfied by the conventional energy technology which utilizes only a few local resources.
Every sector of the Indian economy like agriculture, industry, transport and domestic needs input of energy for the progress and prosperity of nation and societies. Energy is the cornerstone of economic and social development. As a result, the consumption of energy in all forms has been steadily rising all over the world.
The use of conventional energy like coal, oil, and electricity has increased enormously in the last 25 years in ASEAN economies. India is the world’s sixth largest energy consumer, consuming about 3 percent of world’s total energy per year. However, the biomass-based energy meets a major fraction of energy demand in rural areas of the most developing countries, including India. India produces nearly 350 million tonnes of agricultural waste per year (Naidu, 1999). The major residues are cow dung cake, rice husk, coffee husk, coir pith, sugarcane bagasse, sugarcane trash, jute sticks, silk cotton pods, groundnut shells, mustard stalks and cotton stalks.
Biomass as a source of energy is gaining importance as a renewable source that is additionally strengthened as the country’s agriculture is one of the prime sources in the Indian economy. Use of biomass for thermal energy is age-old but the use of “modern biomass” (implying clean combustion process) is more recent. In the last three decades, several biomass-based projects funded by MNRE in the country were developed for high-grade heat or power. In this context, it is necessary that the assessment of biomass availability is made taking account of the present usages in the existing traditional practices and socially essential needs such as fodder, domestic fuel, thatching, and manure.
Biomass has been one of the major energy sources for the mankind ever since the dawn of civilization, although its importance dwindled after the expansion in use of oil and coal in the late 19th century. About 120-150 million metric tonnes per annum of biomass produced by agricultural and forestry residues corresponding to a potential of about 16000 MW.
The briquetting plants have been installed in India since the mid-‘90s, most of them being self-financing briquettors are doing excellent business, especially, in the western and southern regions. A rough estimate says that around 50,000 tonnes of briquettes are consumed annually by the tea industry alone in the state of Tamil Nadu, and 20 000 tonnes by the Indian Tobacco Company in the state of Karnataka. On an average, a typical briquetting plant of die and punch (standard capacity of 750 kg/hr for sawdust) type produces between 250 and 300 tonnes per month which fetch a market price between Rs.1800 per tonne to Rs.2500 (inclusive of transport cost) per tonne. The profit margin is so good that the payback period is well within12 months. Briquettes, when replaced for firewood and coal, provide direct cost savings on the fuel to the tune of 25 percent to 30 percent as the combustion efficiency improves remarkably. In addition to such direct savings are the benefits of easy transportation, handling and storing during rainy seasons besides saving labor for cutting the firewood. These die and punch plants have established their viability and quick return (Babu, 2001).
Charcoal is traditional fuel widely used in many developing countries to meet basic household needs which need to be stopped to conserve forest and wildlife. It is considered as best fuel for most of the traditional cookstoves in many areas and is preferred in the urban areas because of its smoke-free burning. India has 247 billion tonnes of fossils in coal reserves, out of which only 52.24 billion tonnes are extractable reserves. During the 10th plan, coal demand was of 332 million tonnes, while 301 million tonnes were available and 31 million tonnes was the shortage. This shortage is going to be 87 million tonnes during the 12th planMaharashtra. Energy Development Agency has sanctioned 36 biomass-based energy projects with 336 MW capacity so far and the power generated from these projects is expected to be made available in phases in a period of three years.
It has been estimated that 110-150 million tonnes crop residues are surplus to its present utilization as a cattle feed, constructional and industrial raw material and as industrial fuel. Due to their heterogeneous nature, biomass material possesses inherently low bulk densities and thus it is difficult to efficiently and economically handle large quantities of biomass. Therefore, large expenses are incurred during material handling, transportation, storage etc. Transportation had the 2nd highest cost by considering all factors when the biomass power plant was run at full capacity (Kumar et al.2003). It is noted that transportation cost will increase with increasing power plant size. In order to combat the negative handling aspects of bulk biomass, densification is essentially required. If such crop residues are converted into briquettes they can provide a huge and reliable source of feedstock for thermochemical conversion (Anonymous, 2002).
Many of the developing countries produce huge quantities of agro-residues, but they are used inefficiently causing extensive pollution to the environment. The major residues are rice husk, coffee husk, coir pith, jute sticks, bagasse, groundnut shells, mustard stalks and cotton stalks. Sawdust, a milling residue is also available in huge quantity. Apart from the problems of transportation, storage, and handling, the direct burning of loose biomass in conventional grates is associated with very low thermal efficiency and widespread air pollution (Grover and Mishra, 1996).
According to a survey, conducted by the Central government, the potential for power generation from agricultural waste is 16,000 MW in the country and 781 MW in Maharashtra. A high quality densified product is essential to ensure that the positive effects of densification are not mitigated; therefore artificial binding agents are often added to the pre-densified biomass to improve briquette quality. Studies have demonstrated that different biomass grinds bind well without the use of the artificial binding agent. Such feedstock posses natural binding agent that allows them to exhibit preferential qualities after densification. Hence the efficient design and cost-effective densification system improving the feasibility of biomass densification for feed, chemical, and energy production is required. Intensive information is available on wood fuels, but comprehensive data on another kind of biomass or biomass briquettes fuel have not been developed. As such available biomass conversion into densification is a difficult task and extensive research is needed to develop cost-effective and simple technology which is easily accessible to farmers to convert the waste biomass into valuable energy for earning additional returns to make agriculture an energy producing enterprise.
A briquette is a compressed block of coal dust or other combustible biomass material such as charcoal, sawdust, wood chips, peat, rice husk etc.
Types of Briquetting Machine:
- Screw press extruder type briquetting machine
- Hydraulic Piston Press type briquetting machine
- Mechanical Piston Press type briquetting machine
1. Screw Press Extruder type Briquetting Machine:
The screw press extruder type briquetting machine consists of a driving motor, screw, die, and hopper and power transmission system. Pulley and belt are used to transmit power from a motor to the screw. The raw material is fed to the hoppers, which convey it to screw by gravity. The material is pushed forward due to the geometry of screw. As the material is pushed, it is compressed and compressed material comes out of dying in the form of briquettes.
2. Hydraulic Piston Press type Briquetting Machine:
The principle of operation is basically the same as the mechanical piston press. The difference is that the energy to the piston is transmitted from an electric motor via a high-pressure hydraulic oil system. In this way, the machine can be made very compact and light, since the forces are balanced-out in the press-cylinder and not through the frame. The material is fed in front of the press cylinder by a feeding cylinder which often pre-compacts the material with several strokes before the main cylinder is pressurized. The whole operation is controlled by a programme which can be altered depending on the input material and desired product quality. The speed of the press cylinder is much slower with hydraulic press action than with mechanical which results in markedly lower outputs..
3. Mechanical Piston Press type Briquetting Machine:
A reciprocating piston pushes the material into a tapered die where it is compacted and adheres against the material remaining in the die from the previous stroke. A controlled expansion and cooling of the continuous briquette are allowed in a section following the actual die. The briquette leaving this section is still relatively warm and fragile and needs a further length of the cooling track before it can be broken into pieces of the desired length.
Benefits of Briquettes:
- Compacting biomass waste into briquettes reduces the volume by 10 times, making it much easier to store and transport than loose biomass waste The size and shape of briquettes make them easily be stored.
- The compression process allows the briquettes to burn for a lot longer than if it was loose in its original condition.
- Depending on the base material, they produce no or little fly ash. Further, briquettes do not emit gases or any toxic chemicals like sulfur.
- Biomass is the main component in producing briquettes. So where do we get this biomass? Look around you, and there are loads of biomass materials here, there, and everywhere.
- Since briquettes can be domestically made from plants and animal wastes, they are consequently less expensive to produce, and thereby sold at lower prices.
- Briquettes make use of organic materials which are common and renewable. Hence, we have ensured the sustainability of such a fuel source.
- Such units of briquetting could be established in a cluster of villages on mission basis for reducing transport cost of bulky biomass viz. crop residues, sugarcane trash, cotton stalks, sawdust, rice husk, pruned branches and leaves of fruit trees etc. This will enable to give additional income to farmers and at the same time convert the otherwise wasted/carbonized biomass into valuable energy briquettes to mitigate to same extent the energy crisis.
Written by: A. D. Chendake & S. B. Patil
(Pad. Dr. D. Y. Patil College of Agricultural Engineering & Technology, Talsande, Kolhapur)