Industrial Potential For BiogasIntroductionWhat is Bio Gas?Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste. It is a renewable energy source and in many cases exerts a very small carbon footprint.

Biogas compositionThe composition of biogas varies depending upon the origin of the anaerobic digestion process. Landfill gas typically has methane concentrations around 50%.Typical composition of biogas id given below

Compound Formula  %

Methane CH4 50–75

Carbon dioxide CO2 25–50

Nitrogen N2 0–10

Hydrogen H2 0–1

Hydrogen Sulphide H2S 0–3

Oxygen O2 0–0

Source: www.kolumbus.fi

ProductionBiogas is produced as landfill gas (LFG), which is produced by the breakdown of biodegradable waste inside a landfill due to chemical reactions and microbes, or as digested gas, produced inside an anaerobic digester. A biogas plant is the name often given to an anaerobic digester that treats farm wastes or energy crops. It can be produced using anaerobic digesters (air-tight tanks with different configurations). These plants can be fed with energy crops such as maize silage or biodegradable wastes including sewage sludge and food waste. During the process, the microorganisms transform biomass waste into biogas (mainly methane and carbon dioxide) and digestate. The biogas is a renewable energy that can be used for heating, electricity, and many other operations that use a reciprocating internal combustion engine, such as GE Jenbacher or Caterpillar gas engines.[4] Other internal combustion engines such as gas turbines are suitable for the conversion of biogas into both electricity and heat. The digestate is the remaining organic matter that was not transformed into biogas. It can be used as an agricultural fertiliser.

Industrial Potential For BiogasThere are a lot of industries which produce organic waste this waste can processed to produce biogas.

Main industries which can produce biogas are given below

Food-processing industries Live Stock Agriculture Poltery

Food-processing industrial wastesFood processing comprises the methods and techniques used to transform raw ingredients into food; or to transform food into other forms for consumption by humans or animals, either at home or in the food processing industries (Kaushik, et al., 2009). The processes often produce large amounts of wastes, so called byproducts, which have been evaluated in many studies for their potential utilization and their suitability for chemical and biological treatments. Since these by-products contain relatively high concentrations of organic contents, anaerobic digestion is a preferable method for treatment of these materials.

Sugar processing wasteSugar is produced in 121 Countries and the overall global sugar production was approx. 160 million tons in year 2009, which was 4.5% higher than in year 2008 (World sugar market review, 2010). Approximately 70% of sugar is produced from sugar cane, while the remaining 30% is produced from sugar beet. Beetsugar production generates several streams of organic wastes and the process scheme is shown in Figure 2. The circles mark the model wastes from sugar production, used in our research (Paper I, II). The three main waste-streams are molasses, beet pulp and cutoffs (beet top and beet leaves). Molasses is a syrup residue from the sugar extraction process, which can contain up to 48% sugar (Satyawali and Balakrishnan, 2007). Technological advances in the sugar industry have made it possible to extract more sugar from the normal molasses. Desugared molasses is a residue from the desugaring process of normal molasses (Olbrich, 1963). From the factory data (DANISCO, Denmark), every ton of beet sugar produced generates 0.24 ton of DM, 0.33 ton of beet pulp, and 0.53 ton ofgrass cut-offs (Sugar production, 2001)

Potato starch processing wasteWorld potato production is steadily increasing, from 268 million tons in 1991 to 314 million tons in 2008 (FAOSTAT, 2010). Since the 1990s, production has dramatically increased in Asia, Africa and Latin America, with over a fivefold increase in the past 40 years. These countries now account for half of the world’s production, with China and India accounting for one third of the total production.Denmark was the thirteenth largest potato producer in Europe in 2007, typically contributing 1.5-2 million tons per year, depending on the season. 75% of the Danish potatoes are used in potato starch production and 85% of Danish potato starch is exported to more than 40 countries all over the world (International starch institute, 2010). Potato starch production generates several streams of organic wastes and the process scheme is shown in Figure 3. The circles show the model wastes from potato starch production relevant to our research (Paper III). Per ton of potato flour (80% potato starch and 20% water) produced, 6.6 m3 of potato juice and 0.73 ton of potato pulp are produced as by-products (Potato flour production, 2002). These two by-products contain biodegradable components such as starch and proteins, which could be used for biogas production through anaerobic digestion.

Palm oil processing wasteThe production of palm oil is increasing every year since the 1960s. Crude palm oil is the main product in the palm oil industry. However, large amounts of wastes are also generated, such as POME produced through a multistep oil extraction processes, EFB produced after sterilization, and deoiled POME

produced after clarification of POME (Poh and Chong, 2009). Palm oil production generates several streams of organic wastes and the process scheme is shown in Figure 4. The circles mark the model wastes from palm oil production in our research (Paper IV, V). For every ton of palm oil extracted, 2.5 tons of POME and 1.3 tons of empty fruit bunch are generated. At least 44 million tons of POME was produced in Malaysia in year 2008, which led to high demand for proper treatments (Wu et al., 2010)

Potential for biogas and fertilizerBeing an agro-livestock based economy; Pakistan has huge resources of biomass that are available in the form of crop residues, dung and feces, poultry litter, sugarcane bagasse and wood [5]. Electricity generation using biomass is one of the most convenient options, approximately 9 Giga Watts of electricity is generated from biomass worldwide. Pakistan is world’s 5th largest sugarcane producer with an average annual production of 50 million tons cane and 10 million tons of bagasse. According to an estimate there are about 80 sugar mills having potential to generate almost 3000 MW energy through biogas generation but they are currently operating at 700 MW [12].

Livestock sector is growing at the rate of 4% annually [1]. There are almost 159 million animals and their manure can be used for generation of biogas in rural areas. Energy production by using animal feces is highly sustainable as it is economically viable, socially acceptable besides being environment friendly [14]. There are almost 65.2 million cattle and buffalo (Table 2) [1] assuming that an average animal can produce 10 kg of manure daily would account for almost 652 million kg of dung. If 50% of produced feces is collected and used for biogas production, it will be 326 million kg. According to an estimate about 20 kg wet mass of manure can generate 1 cubic meter (m3) biogas [6] therefore producing almost 16.3 million m3 biogas daily. Almost 112 million people in Pakistan are rural residents and biogas can meet their cooking and other energy needs in a good way. Pakistan can also explore biogas potential of citrus pulp, paper industry, slaughter house and street waste as well. Poultry waste is ideal substrate to produce

biogas [15]. Rice straw, when used for biogas production in comparison with other resources like cotton gin, etc. was found best for methane production but when cotton gin mixed with livestock dung was fermented; it produced more gas in lesser time [16]. This clearly states that rice straw and cotton wastes can be used for electricity generation as well [15]. Apart from gas generation Pakistan has potential to produce 21 million tons of bio fertilizer per year [9]. A study shows that manure collected from cow farms has phosphorus value ranging between 4100 and 18,300 mg/kg of dry matter [17]. Another research showed that 57% of total manure produced was collectable and after considering all the losses 19% of the fresh manure nitrogen, 37% of phosphorus and 29% of potassium were available to plants and they could compensate almost 20% of nitrogen and 66% of phosphorus required in the fields [18]. Manure application can surely reduce the costs of chemical fertilizers and enhance the productivity of soil while acting as indirect energy source for the country.

Biogas plant for poultry factories The biogas plant at the poultry factory will significantly reduce the part of energy costs in the prime cost of end products, and also provide enterprise with the energy without the use of external energy sources.Chicken manure is quite aggressive because of the high content of ammoniates. In its raw form, it has a sharp, distinct smell. At the same time, chicken manure is a highly effective organic fertilizer. To obtain such fertilizer, manure must be stored for about a year, which causes a negative reaction of

surrounding communities. In the case of manure processing in a biogas plant, it can be applied as fertilizer at once, without long-term storage and composting it, that significantly reduces the environmental load. Also not processed manure may contain pathogenic flora. After processing in the biogas plant it disappears and active flora appears instead, that improves microbiological processes in the soil.

Key features of chicken manure comparatively with other substrates are high content of protein, which is a source of nitrogen. Therefore, chicken manure in its pure form (mono-substrate) is processed under two stage technology. Biogas plant is equipped by an additional hydrolysis reactor. In the hydrolysis reactor, the special temperature conditions are provided, humidity rises, and PH level is controlled. Also if the technological cycle of biogas plant is designed as closed (liquid fraction after fermentation is used for dilution of fresh raw materials), biogas plant should be equipped by ammonia nitrogen removal system, as it inhibits the process (leads to damping).

Construction of a plant for biogas production from chicken manure will allow the company to become energy-independent, to lower production prime cost and to decide the issue of environmental safety.

Development of energy crop digestionThe idea to use dedicated plant biomass,the so called “energy crops” for methane production (biomethanation) is not new. Early investigations on the biomethanation potential of different crops and plant materials have been carried out in the 1930s by Buswell in the USA and later on in the 1950s by Reinhold and Noack in Germany. In 1980, Stewart described the potential use of oats, grass and straw in New Zealand, resulting in methane yields of 170–280 m3.t-1 TS. Even water hyacinths and fresh water algae were shown to result in medium methane yields between 150–240 m3.t-1 TS. In the USA a large project on microalgae and kelp for aquatic raw material production was started. Although the digestion of crop material was demonstrated, the process was hardly applied in practice. Crop digestion was commonly not considered to be economically feasible. Crops, plants, plant by-products and-waste materials were just added occasionally to stabiliseanaerobic waste digesters. With steadily increasing oil prices and improved legal framework conditions, “energy crop”-research and development was again stimulated in the 1990s. In Germany for example, the number of digesters using energy crops has increased from about 100 in 1990 to nearly 4,000 in 2008 (Figure 1). The steady increase in energy crop digester applications in Germany and similarly in Austria, can be directly attributed to the favourable supportive European and National legal frameworks of eco-tariffs, paid for renewable energy. Depending on the electrical power capacity of the digestion plants, staggered feed in tariffs are guaranteed for the whole depreciation period of the investment. Similar subsidising systems exist for instance in Switzerland and France. Other European countries apply tax exemptions (e.g. Sweden) or certificates (e.g. UK) for renewable energies.

Figure: 1:

Energy crops used in anaerobic digestionNumerous plants and plant materials have been tested for their methane formation potential. In principal many varieties of grass, clover, cereals and maize including whole plants, as well as rape or sunflower proved feasible for methane production. Even hemp, flax, nettle, miscanthus or potatoes, beets, kale, turnip, rhubarb and artichoke were tested successfully. Some practically used “energy crops” are shown in photos 1 to 4.