Biogas Nord to make biomethane from bagasse in India

German biomethane company Biogas Nord AG has received [*German] its second order from a large sugar mill in India's Maharashtra state. An Indian delegation led by Suryakanta Patil, the state's Agriculture Secretary, visited the company in Bielefeld to sign the €1.8 million deal. In March of this year, Biogas Nord received its first major in India while on tour in the country with Christina Thoben, Minister for Economic Affairs of the state of Nordrhein-Westfalen (earlier post).

Operational Biogas Nord plants are located predominantly in Northern and Eastern Germany but demand from oustide the country is growing rapidly. The listed company's innovative technologies have allowed it to build a portfolio that includes large-scale plants in Thailand, Cuba, Chile and Peru.

Large potential
In Maharashtra, Biogas Nord will start construction of four anaerobic digesters that will convert sugarcane bagasse - the crushed canes from which the juice has been extracted - into the carbon neutral gas. Work will start next month.

India has the world's second largest sugar industry, producing some 14 million tonnes per year grown on 3.6 million hectares of land. A total of 165 sugar mills are located in Maharashtra alone, more than half of all large facilities in India (map, click to enlarge). The state also hosts the largest number of sugarcane ethanol plants.

Not only is the sugar industry a symbol of national pride in India, it is an economically vital sector. Large numbers of rural people make a living from growing sugarcane to supply the large sugar factories of the country. We are pleased to have built trust amongst the stakeholders in the sector in Maharashtra. This may open a series of offers to us. - Gerrit Holz, CEO of Biogas Nord AG

The planned biogas facilities will process around 100 tonnes of organic waste per day. Four digesters will ferment the processing residues into biogas, that will be upgraded to natural gas quality bio-methane. This fuel will then be used to power CNG vehicles. Traditionally, bagasse is burned as a solid biofuel for power and electricity, but converting it into biogas allows the energy contained in it to be used as a transport fuel.

The sludge from the biogas digesters will in turn be used as an organic fertiliser on the sugar plantations that supply the mill. The biogas plant will both power the sugar mill as well as vehicles used by the factory, replacing all its fossil fuel needs. This is possible because the production of sugar yields such a large stream of residual biomass that contains a lot of energy. Biogas Nord delivers, installs and operates the entire facility.

Optimized technology
Large-scale biogas technology is in its infancy in India but is finding a growing interest in several industrial sectors. "Besides our strong portfolio in Europe we see the Indian market as one with a lot of growth potential. More orders are on the table", says Dr. Holger Schmitz.

The biogas plants installed by Biogas Nord are based on a flow-storage process (chart, click to enlarge). This involves the operation of several tanks with substrate continuously flowing through them:
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The addition of substrate into the fermenter (first tank) raises the level of the sludge and the putrefied sludge flows through the overflow into the next tank. This process is repeated if there is another tank connected to the second tank. The tanks we build are upright, cylindrical tanks made of reinforced concrete. The size, number and equipment of the tanks/fermenters depends on the type and amount of substrate to be treated. Where possible, existing tanks are integrated into the plant design.

A sump is installed in order to mix the individual substrates and ensure that the fermenter is continuously filled. Here, too, existing sumps are incorporated into the planning of the plant.

Pumps, screw conveyors or similar conveying equipment is used to feed the raw materials into the fermenter. The choice of conveying equipment depends on the type and amount of substrate to be fermented. Most of the biogas plants are equipped with a separate solids feeder.

Some substrates have to be sanitised before being spread onto agricultural land. For this purpose the substrate (prior to fermentation) or the entire digested sludge is heated to a specified temperature for a certain period of time.

All tanks can be fitted with up to four mixing devices depending on the type and amount of substrate to be treated and the size of the tank. Fermenters and secondary fermenters are fitted with double-membrane roofs for gas storage. The inner membrane serves as a gas holder and the outer membrane as protection against the weather. Between the two membranes a slight pressure is built up with a compressor, which gives the outer membrane its dimensional stability while at the same time applying pressure to the gas holder.

At Biogas Nord the second tank is called a secondary fermenter if it is fitted with a double membrane for gas storage, otherwise it is a storage tank. As a rule, wall and floor heating is installed in fermenters and secondary fermenters. The heating tubes are laid in the concrete. The outer walls of the fermenter and secondary fermenter are heat insulated and, as a final step, clad with trapezoidal panels.

The hydrogen sulphide content in the biogas produced is normally reduced with an integrated desulphurisation unit in the gas holder. At the request of the customer Biogas Nord can also install our specially developed external desulphurisation system.

After purification, the biogas is converted into electrical and thermal energy in a combined heat and power plant (CHP). Some of the electrical energy is used to cover the electricity requirements of the biogas plant. Some of the thermal energy generated is used as process energy for heating the fermenter and secondary fermenter. The surplus can be used to heat dwelling houses and stables as well as for agricultural and industrial processes with a particular requirement for heat.

In Europe
The past few years have brought a very rapid development of the biogas sector in the EU, especially in Central Europe. There the gas is being fed into secondary natural gas grids (with the option of feeding it in the mains being studied by the EU), used increasingly as a clean transport fuel, and positioned as a starting point for the creation of biorefineries. Dedicated energy crops are being developed. The gas is also being used on an experimental scale in highly efficient fuel cells. An overview of these developments can be found here (a search in the technorati search engine will reveal several newer developments).

The green gas has a very large potential in the EU, with some estimates indicating that it could replace all imports of Russian natural gas by 2030 (earlier post). If burned for the generation of electricity in power plants with socalled carbon capture and storage (CCS) infrastructures, biogas can become radically carbon negative. This means its use can take past CO2 emissions out of the atmosphere (earlier post).

Map: sugar mills, ethanol plants and cogeneration units in Maharasthra. Courtesy: Indian Sugar Mills Association.

More information:
Raffeisen: Biogas Nord erhält weiteren Auftrag aus Indien - June 15.