Briquetting is a way to make use of biomass residues that would otherwise go to waste, and replace the use of wood and charcoal (often produced unsustainably) as well as fossil fuels, thus cutting greenhouse gas emissions.
Briquetting is a compaction technology that has been around for many years. Fines are pushed into the nip of two counter-rotating wheels using a screw or gravity feeder. High hydraulic pressure is applied and the rotating wheels compress the feed between the pockets to form briquettes. Unlike pelletization, briquetting does not always require a binder, but generally some amount of molasses, starch, or tar pitch is used. A traditional application for briquetting is the agglomeration of coal.
Most applications of briquetting in the iron and steel industry involve waste materials, such as mill scale and process dusts, sludges, and filter cakes . In the DR industry, a number of facilities briquette their hot DRI product to produce a higher-density product for safer shipping. This material is known as HBI (hot briquetted iron), as discussed in Section 1.2.3.
Briquetting machines, with dies and punches, driven by a single bullock, have been developed by the School of Applied Research in Maharashtra, India. They cost about US$ 2400 each. The machine is very sturdy but the problem is the limited maximum production 25 kg/hr and the price of the equipment.
The same school has also developed a briquetting machine with two plungers driven by a 3 horse powermotor. The maximum capacity is 100 kg/hr and the price about US$ 4000. However, the pressure on the briquettes is not very high and it is necessary either to use a binder or to handle the briquettes with great care.
GAKO-Spezialmaschenen in West Germany produces briquetting equipment that uses the piston extruder compacting method and produces good quality briquettes because of the high pressure although this results in higher prices and power consumption. A 150 kg/hr machine costs about US$ 12 900 and a 60 kg/hr machine about US$ 8800 and requires a power load of 8.5 kW.
T & P Intertrade Corporation Ltd in Thailand markets a press-screw system briquetter that heats the agro-waste before compression. This means that good briquettes can be produced without needing a binder and at lower pressure, resulting in cheaper equipment. Their Ecofumac has a capacity of about 150 kg/hr, needs a 15 hp motor and three 2000 watt heaters and costs about US$ 5850. The grinder needs a 5 hp motor. Unfortunately a lot of energy is used by the heaters and there have also been some problems with other components.
It can be seen, therefore, that even if equipment does exist, the problems are not totally solved. Either equipment is too expensive with little capacity and too high an energy use, or poor quality briquettes result. There is still a need for a medium-size briquetting machine that is inexpensive, easy to operate, repairable using local tools and commonsense, energy efficient, reliable and which can handle different types of raw material. The advantage of medium-sized equipment is that capital investment is low and mechanized drying and special storage space is not required. In addition it would be practical for use in villages and in places with small wood industries or small agro-industries like groundnut oil mills, sugar mills, saw mills and paper mills. The briquettes could be used locally in bakeries, brickworks, potteries, curing houses, breweries, drieries or simply for cooking.
Briquetting is like pelletising a process in which the raw material is compressed under high pressure, which causes the lignin in the wood or biomass to be liberated so that it binds the material into a firm briquette.
The most appropriate water content in the raw material for briquetting varies and depends on the raw material. However, the normal water content is between 6% and 16%. If the water content is over 16% the quality of the briquettes will be reduced, or the process will not be possible.
There are hydraulic presses for small capacities from 50 to 400kg/hour. The raw material is fed into the press by a time-controlled dosing screw, which means that it is the volume of the raw material and not the weight, which is controlled. Briquettes have a fairly good uniform length (square briquettes) and they are mainly used by domestic consumers.
Mechanical presses are available with capacities from 200kg/hour up to 1800kg/hour. Briquettes from these presses are normally round and short and they are used in heating plants for larger industries and for district heating plants. A mechanical press is built like an eccentric press. A constantly rotating eccentric connected to a press piston presses the raw material through a conic nozzle. The required counter pressure can be adjusted only by using a nozzle with a different conicity. A mechanical press receives raw material from a speed-controlled dosing screw. The speed of the dosing screw determines the production rate of the press. A change in the specific gravity of the raw material will change the hardness of the briquettes. A mechanical briquetting press will produce a long length of material a briquette string which, however, breaks into random lengths depending on the binding capacity of the raw material. A saw or cutter is used to cut the briquette string into briquettes of uniform length.
The briquette string pushed out of the press is very hot because of the friction in the nozzle. The quality of the briquettes depends mainly on the cooling and transport line mounted on the press. A cooling/transport line of at least 15m is recommended for wood briquettes. The longer the time a briquette remains in the cooling line the harder it will become. Cooling lines up to 50m long are common.
Biomass briquetting technology can compress some biomass raw materials, such as wood shavings, sawdust, crop straw, and other solid waste biomass fuel through pressurizing and heating. It is conducive to the transportation, storage and combustion and can largely improve the efficiency of combustion and fuel utilization. At present, there are three main types of solid shaping, including screw extrusion, piston punch, and roller forming.
Thermochemical conversion involves biomass structure degradation with oxygenic or anoxygenic atmosphere at high temperature . It includes three kinds of technology, namely biomass gasification, biomass pyrolysis, and direct liquefaction.
Biomass gasification is a chemical reaction process that reacts with gasifying agent (air, oxygen, and water) at high temperatures in gasifiers. The main problem of biomass gasification technology is that the tar obtained in the gasification of gas is difficult to purify, which has become the main factor restricting the biomass gasification technology.
Pyrolysis is a thermal process in which the organic polymer molecules in the biomass are quickly broken into short chain molecules, coke, bio-oil and noncondensable gas in the absence of oxygen or a small amount of oxygen under high temperatures. Biomass liquid fuel could provide an alternative to petroleum up to a certain extent. After some modification, industrial oil fired boilers and internal combustion engines can use bio-oil as fuel directly.
Burning biomass to obtain heat energy, as a direct utilization mode, has been more and more widely employed based on the mature experiences during development of fossil fuel power plants. When biomass is used as the boiler fuel, its thermal efficiency is close to the level of fossil fuels. Compared with fossil fuels, for example, coal, biomass fuel contains more hydrogen element, is more volatile, and has less carbon and sulfur content.
Bioconversion technology of biomass refers to the process by which microorganisms produce high-grade energy through biochemical action with agricultural and forestry wastes. Anaerobic fermentation and ethanol fermentation are the two main conversion types. With the help of anaerobic bacteria, organic matter can be converted to combustible gas, for example, methane under a certain temperature, humidity, pH, and anoxygenic conditions. The ethanol is produced by microzyme with the carbohydrate hydrolyzed by enzymes.
Renewed interest in briquetting coal has arisen because of (i) the increasing amounts of fine coal being generated in mining and preparation which are stockpiled or disposed of in tailings dams and lead to uneconomic land use and environmental problems; (ii) the need for easily handled and convenient coal products; and (iii) the demand for smokeless solid fuels.
Briquette quality depends on composition (type of coal and binder), particle sizes and processing conditions. In this study various data are presented on the influences of such factors on mechanical strength and water resistance of briquettes formed from high rank coals using a molasses/lime binder alone and also including bagasse. These data relate to Hardgrove grindability index (HGI), coal size, moisture and curing time.
White Energy developed the BCB technology at pilot scale in Australia, after initial work by CSIRO. In partnership with Bayan Group, White Energy formed PT Kaltim Supa Coal, and constructed a commercial scale 1 Mtpa plant at Tabang in East Kalimantan. The BCB process takes 4200 kcal/kg GAR feed and produces a 6100 GAR product. Its difference from Kobelcos UBC process is that BCB does not use any binder to reconstitute the dried product.
This project has been terminated due to commercial differences between the partners. The financial model used a sub-20 coal price delivered from mine mouth to plant. Bayan Group changed the price to follow the Indonesian Reference Price which more than doubles the feedstock cost. The parties are in negotiations to settle the dispute (White Energy, 2011).
Generally, briquette manufacture (briquetting) involves the collection of combustible materials that are not usable as such because of their low density, and compressing them into a solid fuel product of any convenient shape that can be burned like wood or charcoal. Thus the material is compressed to form a product of higher bulk density, lower moisture content, and uniform size, shape, and material properties. Briquettes are easier to package and store, cheaper to transport, more convenient to use, and their burning characteristics are better than those of the original organic waste material.
The raw material of a briquette must bind during compression; otherwise, when the briquette is removed from the mold, it will crumble. Improved cohesion can be obtained with a binder but also without, since under high temperature and pressure, some materials such as wood bind naturally. A binder must not cause smoke or gummy deposits, while the creation of excess dust must also be avoided. Two different sorts of binders may be employed. Combustible binders are prepared from natural or synthetic resins, animal manure or treated, dewatered sewage sludge. Noncombustible binders include clay, cement, and other adhesive minerals. Although combustible binders are preferable, noncombustible binders may be suitable if used in sufficiently low concentrations. For example, if organic waste is mixed with too much clay, the briquettes will not easily ignite or burn uniformly. Suitable binders include starch (5%10% w/w) or molasses (15%25% w/w) although their use can prove expensive. It is important to identify additional, inexpensive materials to serve as briquette binders in Kenya and their optimum concentrations. The exact method of preparation depends upon the material being briquetted as illustrated in the following three cases of compressing sugar bagasse, sawdust, and urban waste into cooking briquettes.
Rural villages in developing countries are connected to the drinking water supply without a sewer system. Other places in urban and semi-urban communities have no sewage treatment networks. Instead under each dwelling there is a constructed septic tank where sewage is collected or connected directly to the nearest canal through a PVC pipe. Some dwellings pump their sewage from the septic tank to a sewer car once or twice a week and dump it elsewhere, usually at a remote location.
In general, a huge amount of sewage and solid waste, both municipal and agricultural are generated in these villages. Because of the lack of a sewer system and municipal solid waste collection system, sewage as well as garbage are discharged in the water canals. This and the burning of agricultural waste in the field cause soil, water, and air pollution as well as health problems. Some canals are used for irrigation, other canals are used as a source of water for drinking.
Rural communities have had agricultural traditions for thousands of years and future plans for expansion. In order to combine the old traditions with modern technologies to achieve sustainable development, waste should be treated as a byproduct. The main problems facing rural areas nowadays are agricultural wastes, sewage, and municipal solid waste. These represent a crisis for sustainable development in rural villages and to the national economy. However, few studies have been conducted on the utilization of agricultural waste for composting and/or animal fodder but none of them has been implemented in a sustainable form. This chapter combines all major sources of pollution/wastes generated in rural areas in one complex called an eco-rural park (ERP) or environmentally balanced rural waste complex (EBRWC) to produce fertilizer, energy, animal fodder, and other products according to market and need.
The idea of an integrated complex is to combine the above-mentioned technologies under one roof, a facility that will help utilize each agricultural waste with the most suitable technique that suits the characteristics and shape of the waste. The main point of this complex is the distribution of the wastes among the basic four techniques animal fodder, briquetting, biogas, and composting (ABBC) as this can vary from one village to another according to the need and market for the outputs. The complex is flexible and the amount of the outputs from soil conditioner, briquettes, and animal food can be controlled each year according to the resources and the need.
Based on the above criteria, an environmentally balanced rural waste complex (EBRWC) will combine all wastes generated in rural areas in one complex to produce valuable products such as briquettes, biogas, composting, animal fodder, and other recycling techniques for solid wastes, depending upon the availability of wastes and according to demand and need.
The flow diagram describing the flow of materials from waste to product is shown in Figure 7.2. First, the agricultural waste is collected, shredded, and stored to guarantee continuous supply of waste into the complex. Then according to the desired outputs the agricultural wastes are distributed among the basic four techniques. The biogas should be designed to produce enough electrical energy for the complex; the secondary output of biogas (slurry) is mixed with the composting pile to add some humidity and improve the quality of the compost. And finally briquettes, animal feed, and compost are main outputs of the complex.
The environmentally balanced rural waste complex (EBRWC) shown in Figure 7.3 can be defined as a selective collection of compatible activities located together in one area (complex) to minimize (or prevent) environmental impacts and treatment cost for sewage, municipal solid waste, and agricultural waste. A typical example of such a rural waste complex consists of several compatible techniques such as animal fodder, briquetting, anaerobic digestion (biogas), composting, and other recycling techniques for solid wastes located together within the rural waste complex. Thus, EBRWC is a self-sustained unit that draws all its inputs from within the rural wastes achieving zero waste and pollution. However, some emission might be released to the atmosphere, but this emission level would be significantly much less than the emission from the raw waste coming to the rural waste complex.
The core of EBRWC is material recovery through recycling. A typical rural waste complex would utilize all agricultural waste, sewage, and municipal solid waste as sources of energy, fertilizer, animal fodder, and other products depending on the constituent of municipal solid waste. In other words, all the unusable wastes will be used as a raw material for a valuable product according to demand and need within the rural waste complex. Thus a rural waste complex will consist of a number of such compatible activities, the waste of one being used as raw materials for the others generating no external waste from the complex. This technique will produce different products as well as keep the rural environment free of pollution from the agricultural waste, sewage, and solid waste. The main advantage of the complex is to help the national economy for sustainable development in rural areas.
A collection and transportation system is the most important component in the integrated complex of agricultural waste and sewage utilization. This is due to the uneven distribution of agricultural waste that depends on the harvesting season. This waste needs to be collected, shredded, and stored in the shortest period of time to avoid occupying agricultural lands, and the spread of disease and fire.
Sewage does not cause transportation problems as it is transported through underground pipes from the main sewage pipe of the village to the system. Sewage can also be transported by sewage car which is most common in rural areas since pipelines may prove expensive.
Household municipal solid waste represents a crisis for rural areas where people dump their waste in the water canals causing water pollution or burn it on the street causing air pollution. The household municipal solid waste consists of organic materials, paper and cardboard, plastic waste, tin cans, aluminum cans, textile, glass, and dust. The quantity changes from one rural community to another. It is very difficult to establish recycling facilities in rural areas where the quantities are small and change from one place to another. It is recommended to have a transfer station(s) located in each community to separate the wastes, and compact and transfer them to the nearest recycling center as explained in Chapter 5. The transfer station consists of a sorting conveyer belt that sorts all valuable wastes from the organic waste, which is then compacted by a hydraulic press. The collected organic waste can be mixed with other rural waste for composting or biogas as explained above.
The outputs of the EBRWC are valuable and needed goods. EBRWC is flexible and can be adjusted with proper calculations to suit every village; moreover inputs and outputs from the complex can be adjusted every year according to the main crops cultivated in the village, which usually varies from year to year. The key element to the success of this solution lies in the integration of these ABBC technologies to guarantee that each type of waste is most efficiently utilized.
The four corner stone technologies for agricultural waste are animal fodder, briquetting, biogas, and composting (ABBC technologies). These technologies can be developed based on demand and need. In principal three agricultural waste recycling techniques can be selected to be the most suitable for the developing communities. These are animal fodder and energy in a solid form (briquetting) or gaseous form (biogas) and composting for land reclamation. There are some other techniques, which might be suitable for different countries according to the needs such as gasification, fiber boards, pyrolysis, etc. These techniques might be integrated into a complex that combine them altogether to allow 100% recycling for the agricultural waste. Such a complex can be part of the infrastructure of every village or community. Not only does it allow to get rid of the harms of the current practice of agricultural waste, but also of great economical benefit.
The amount of agricultural waste varies from one country to another according to type of crops and farming land. These waste occupies the agricultural lands for days and weeks until the simple farmers get rid of these waste by either burning it in the fields or storing it in the roofs of their houses; the thing that affects the environment and allows fire villages and spread of diseases. The main crops responsible for most of these agricultural wastes are the rice, wheat, cotton, corn, etc. These crops were studied and three agricultural waste recycling techniques were set to be the most suitable for these crops. The first technology is animal fodder that allows the transformation of agricultural waste into animal food by increasing the digestibility and the nutritional value. The second technology is energy, which converts agricultural wastes into energy in a solid form (briquetting) or gaseous form (biogas). The briquetting technology that allows the transformation of agricultural waste into briquettes that can be used as useful fuel for local or industrial stoves. The biogas technology can combine both agricultural waste and municipal waste water (sewage) in producing biogas that can be used in generating electricity, as well as organic fertilizer. The last technology is composting, that uses aerobic fermentation methods to change agricultural waste or any organic waste into soil conditioner. The soil conditioner can be converted into organic fertilizer by adding natural rocks to control N: P: K ratio, as explained before. Agricultural waste varies in type, characteristics and shape, thus for each type of agricultural waste there is the most suitable technique as shown in Figure 13.28.
A complex combining these four techniques is very important to guarantee each waste has been most efficiently utilized in producing beneficial outputs like compost, animal food, briquettes and electricity. Having this complex will not only help the utilization of agricultural waste, it will help solving the sewage problem as well that face most of the developing countries, as a certain percentage of the sewage will be used in the biogas production and composting techniques to adjust carbon to nitrogen ratio. An efficient collection system should be well designed to collect the agricultural waste from the lands to the complex in the least time possible to avoid having these wastes occupying agricultural land. These wastes are to be shredded and stored in the complex to maintain continuous supply of agricultural waste to the system and in turns continuous outputs.
It is generally accepted that the main route for human pharmaceuticals to the aquatic environment is via sewage treatment plants receiving wastewater from households and hospitals. We have analysed pharmaceuticals in the effluent from a wastewater treatment plant serving about 90 bulk drug manufacturers in Patancheru, near Hyderabad, Indiaa major production site of generic drugs for the world market. The samples contained by far the highest levels of pharmaceuticals reported in any effluent. The high levels of several broad-spectrum antibiotics raise concerns about resistance development. The concentration of the most abundant drug, ciprofloxacin (up to 31,000g/L) exceeds levels toxic to some bacteria by over 1000-fold. The results from the present study call for an increased focus on the potential release of active pharmaceutical ingredients from production facilities in different regions.