TECHNOLOGY

 

Which technology did we choose?

Technology that we like to propose is Mechanical Biological Treatment Plant. This technology can produce various useable materials from landfill through the separation process of municipal solid waste. Besides that, it can convert organic waste into electricity and rich organic fertilizers which is our main objective.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Diagram above show us the block diagram of Mechanical Biological Treatment Plant(MBT). A MBT plant contains two systems. Moreover, MBT plant contains Municipal Solid Waste Separation Plant and a patented horizontal Dry Anaerobic Digester Plant. Then, MBT plant can separate municipal solid waste into 5 types of different materials which are organics, plastics, ferrous metals, papers and inert materials. Besides that, by operate AGE’s recycling technologies, we can convert organic waste into electric energy, heat energy, organic fertilizers, and other sustainable resources as shown in the diagram. 

 

Besides that, our main focus is dry anaerobic digestion which is biogas production in this process. After the separation of raw materials from garbage, organic waste will send into a bunker by an automate crane. Then, the organic waste will be shredded for processing. Next, digester/fermenter will be loaded with organic waste. In order to maintain the process condition, digester hatch device is closed with a gas seal. Moreover, after the door is sealed, infloor aeration system will activate instantaneously. The function of aeration system is creating aerobic conditions by pumps outside air into the organic waste material before the anaerobic reaction takes place.

 

Next, organic waste is sprayed with modified process water containing thermophilic micro-organisms(percolate) that decompose the waste and produce biogas under anaerobic condition. Moreover, few drops of percolate on the material can cause production of biogas within 20 days. Moreover, in order to ensure proper pH balance, high amount of organic acids produced during the beginning of the process will be stored and degraded in percolate tank. Hence, the production of biogas will speed up after percolation. 

 

Why did we choose this process?

My group has chosen the technology which consist of the process, thermophilic dry anaerobic digestion . As mentioned above about this process, the objective for this plant is to separate municipal solid waste into useable products, rather than creating landfills. The product obtained is converted into electricity and organic fertilizer, which is our main product. There are few reasons on why we have chosen this technology.

 

The first notable reason is of course, for the products it gives. This process gives out two main products, biogas ( methane gas ) and fertilizers. Using only municipal solid waste, getting these two products makes this process a very strong, if not definite process to be chosen. This is because the biogas given out can be used for production of energy, in forms of electricity and heat. Biogas can also be used for gas powered vehicles as fuels .The fertilizers which comes out in liquid and solid form can be used for agricultural purposes, making this process very good in terms of economy.

 

Effect on nature was also considered and this was process was confirmed to be an eco-friendly process. Compost and liquid fertilizers generated will be incorporated back into soils, reducing the soil’s depletion rate. Thus completing the ecological cycle and chemical fertilizers also is saved this way. Reduced air and water pollution is another key factor in contributing towards saving mother earth.

Dry anaerobic process is the key factor in delivering the products mentioned above and was the strong factor for choosing this technology. Although this process has many advantages, the ones related to our products will be specified in detail. These advantages are :  nutrient retention, pollution control, odour reduction, economic benefits, scalable technology, developing country application and fuel based renewal.

 

Anaerobic process is mostly used around the world as a source of renewable energy, which means this ensures an economical process. With the re-use of waste being a viable option for anaerobic process, this makes it to be a low capital cost process. The waste products are usually in high content of nutrients, but some process may tend to destroy such nutrients, which is essential for plants if the waste is to be converted into fertilisers. This process increases the amount of nitrogen present as ammonia, thus when made into fertilizers it will contain more nitrogen making it a highly nutrient fertilizer.

 

This process is said to be scalable, meaning it can be done with a small plant at small land, or can be made in a huge place with a huge plant for maximizing the efficiency and products. This process has no critical mass required, meaning it can be done by a developing country. This can be used to serve the local community because a small amount of waste can produce a large amount of biogas.

Fuel based renewal also is affected here, as this process’s end product is biogas(Stuart.P,n.d). Peak production is the suitable term used here. Storage tank and plant size is directly proportional, a bigger plant will have a bigger storage tank. Fuel can be stored as much as possible (peak production) ,which also can be related to maximizing efficiency. Landfills or spreading of raw slurries on land creates an unpleasant smell. Unpleasant smell ranges from ammonia up to sulphides. Anaerobic process can reduce this odour by at least 80% at a minimal, which is considered very good compared to conventional methods.

 

Thermophilic condition was chosen for dry anaerobic digestive process. There are two types as mentioned above, thermophilic meaning high temperature and mesophilic meaning low temperature. The ranges of temperature in Celsius for thermophilic is from 50-60 Celcius, and mesophilic ranges from 30-40Celcius. Study shows that thermophilic gives the same amount of fertilizers as mesophilic reaction, but in a shorter amount of time. Although one may argue that thermophilic requires more energy due to the fact of higher temperature requirement, the energy produced from this process can be re-cycled to make up for the slight increased requirement of energy. The amount of gas produced however, is more for thermophilic reaction rather than mesophilic, with thermophilic having around 25% extra methane than mesophilic.

 

According to the process mentioned above, we chose dry anaerobic digestive system and not wet. The reason for this is because dry anaerobic digestive system has some advantages compared to the wet one.Dry process allows any kind of solid waste to be digested, unlike wet which allows clean organic waste which is pumpable. The flexibility for processing efficiency and tolerance to impurities for wet is low for both, whereas for dry it is high, making dry a preferred condition when using anaerobic process. Dry and wet both have three by-products, with the both having digestate and biogas, and dry having compost whereas wet has sludge. Considering we need compost, it is obvious that dry is the preferred kind of process.

 

Based on the points shown, this technology chosen is made up of the process : thermophilic dry anaerobic digestive process. The process has its benefit which can contribute towards this technology of treating the waste into useable products, which can be beneficial to the society and the organisation itself.

 

Sustainability

            Well, the technology we choose is sustainable energy in between social, environment and economy. MBT plant use Anaerobic Digestion technology which reduce air and water pollution. Moreover, MBT plant use Lyfpod Dry AD system which can generate heat and electricity and also can remove waste that will cause pollution and disease. Besides that, MBT plant have purifier that will purify odour of exhaust fumes from bio-waste fermenter by 95%. Next, the operating noise of a Lyfpod plant is under EU emission limits.

 

            By using this technology, MBT plant more economical than other plants. Lyfpod which generate biogas can reduce waste disposal costs for users, government and commercial bodies. Then, we add on compenets to an existing Lyfpod plant easily and effieciently due to the modular structure of the plant. Furthermore, for a 100, 000 tonnes/annum plant, 0.7 hectares of land space is required which it save a lot space! Next, they use computer system to run the operations of the plant which can enhance system operations and also lower operational costs. Moreover, if wireless connection is available, systems can monitored remotely.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Besides that, table above shows 72,000 tonnes of organic waste loaded in fermenter per year while 197 tonnes per day. This table shows huge amount of organic waste use for the production of biogas which is 8,710,800 Nm3 per year. Moreover, out of 72,000 from organic waste, 57600 tonnes of solid and liquid fertilizer produced per year. This shows that we can convert these organic waste into fertilizer and biogas which show sustainability in environment. Furthermore, we can recycle a lot municipal solid waste from landfill and also reduce air pollution that cause by landfill. Besides that, this technology also considered as economic sustainable because we recycle municipal solid waste which only cost the production cost of biogas and fertilizer.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Catalyst

For this process, there are many kinds of catalyst that can be used to enhance it. Such catalyst are solids such as powdered leaves of some plants, microbial strains such as enzymes, and also inorganic additives such as metals. For this process, we have chosen inorganic additives, also known as metals. The reason for this is because the metals have a better rate of biogas production compared to the other two types of catalyst, and the metals are relatively easy to obtain. 

 

The choice of metal that we have chosen for this process is nickel ion. Nickel ions of various concentrations (2.5ppm or 5ppm) both can be used to enhance production of biogas. A study showed that up to 54% of biogas production can be enhanced by the use of nickel ions,  due to the Ni-dependent enzymes involved in biogas production. The amount of nickel required is usually dependent on the size of reactor, but the exact amount can be said to be close to 0.003mg/g acetate produced respectively(Metcalf and Eddy,2003).

 

References

Chaudhary,B.K.(May 2008).Dry Continuous Anaerobic Digestion Of Municipal

            Solid Waste In Thermophilic Conditions.Asian Institute of Technology,pp.17-18.

            Retrieved July 16th 2015 from

             http://www.faculty.ait.asia/visu/Data/AIT- Thesis/Master%20Thesis%20final/Binod.pdf.

 

Mechanical Biological Treatment plant(n.d). Retrieved July 16th 2015 from

             http://advaitaa.in/green_energy/mbt_plant.html.

 

Metcalf and Eddy(2003).Wastewater Engineering:Treatment and Reuse,4th ed.McGram Hill,

New York.Retrieved July 16th 2015 from  http://www.theecoambassador.com/AnaerobicDigestionProcessParameters.html.

 

Methods comparison (n.d). Retrieved July 16th 2015 from

        http://www.aikantechnology.com/documentation/method-comparisons.html.

 

Santosh,Sangeeta Kohli,T.R.Sreekrishnan et al.(2003,August 18th).  Enhancement of biogas

            Production from solid substrates using different techniques, p.3.

 

Stuart,P.(n.d). The Advantages and Disadvantages of Anaerobic Digestion as Renewable Energy

            Source, pp.3-5 .

 

The benefits of Anaerobic Digestion(2010). Retrieved July 16th 2015 from http://www.streambioenergy.ie/benfits-of-anaerobic.html.