POME Sludge Pellet

Processing palm oil mill effluent (POME) is one of the mandatory requirements for palm oil mills. This requirement becomes a criterion whether the palm oil mill in question has a good environmental concern, especially its waste processing sector. The liquid waste of oil palm mills is one of the large quantities of palm oil mill waste. Almost all palm oil mills always have wastewater treatment ponds. Every ton of FFB (Fresh Fruit Bunch) produces 700 liters (0.7 m3) of liquid waste so that if the plant has a capacity of 60 tons / hour FFB and operates 20 hours per day, the volume of liquid waste produced reaches 42,000 liters / hour (42 m3 / hour) or 800,000 liters / day (800 m3 / day). The method of processing wastewater can be like the diagram below.

Biosolid in the form of accumulated sludge can be processed further for biogas production, with by-products in the form of treated sludge, which is usually an organic fertilizer, can also be directly used as fuel. Instead of just being thrown away, the biosolid can be biomass densified into pellets. By becoming a pellet besides facilitating handling, storage, transportation and utilization. The pellet production process from POME sludge is also almost the same as the production of wood pellets. The production of POME sludge pellets is also a solution to overcome organic waste effectively and cheaper than processed further into biogas. Biogas production from POME with both the covered lagoon and CSTR (stirred tank continuous reactor) still requires expensive investment, so there are still very few oil mills in Indonesia that do it. And if the POME sludge is left alone in the waste pond so that there is aerobic fermentation it will produce methane gas which damages the ozone layer in the atmosphere.

If every month from a palm oil mill is produced 2,000 tons of POME sludge and an area such as Riau which has around 300 palm oil mills, then the potential of POME sludge reaches 600,000 tons and this is equivalent to 300,000 tons of POME sludge pellet. Whereas if calculated nationally with the number of oil mills reaching 1,000 units, the potential of POME sludge will reach 2,000,000 tons or equivalent to 1,000,000 tons of POME sludge pellet. Interestingly, POME sludge pellets also have a fairly high calorific value, which is about 4000 kcal / kg. This can happen because POME sludge still contains palm oil. With such a high calorie content, the POME sludge pellets are attractive. Besides being able to be used by various industries as fuel, the selling price of POME sludge should also be quite attractive because of its high energy content. The hope is POME sludge pellet will become a new and renewable energy amount that is very abundant in Indonesia. And if it is used as industrial fuel which means substituting fossil fuels, then it also reduces the use of fossil fuels, is environmentally friendly and carbon neutral.

Biogas, a Big Potential That is Still Not Much Glimpsed

The main purpose of processing liquid waste that is rich in organic materials is to get clean water both used again (re-use) and disposed of. Biogas products are produced mainly for processing large-capacity liquid waste. The processing stage consists of two stages namely primary and secondary processing. In primary processing, primary sludge will be produced from clarifier or settling tank. The liquid waste is passed to the clarifier or settling tank and the sludge deposit is produced. While in secondary processing, liquid waste is aerated to stimulate microbial growth. These microbes form a floc and settle into secondary sludge. The sludge or sediment must be treated at that location or transported to another place to be processed or disposed of.

The sludge processing unit usually consists of two or four stages. In sludge processing units, small capacity usually consists of only two stages, while large capacity can consist of a total of four stages. The stages of the process are: thickening, digestion (fermentation), dewatering (drying) and sterilization. In the processing unit, small capacity usually only consists of thickening and dewatering, then sludge is further processed elsewhere. Sterilization is only done when there are rules or orders to do it, so it is not done much. In large capacity processing units, the concentrated sludge is then anaerobically fermented to break down complex compounds with the help of microbes, reduce solid volatile and pathogens in the sludge, and simultaneously reduce the occurrence of foul odors.

The sludge fermentation produces biogas. Biogas production depends on sludge composition, residence time in fermentation equipment / digester, temperature and speed of microbial metabolism, which is carefully controlled. If the amount of biogas produced is only small, it is usually only flared or heated in the digester. Whereas if the amount of biogas produced is quite large, it can be used for cogeneration fuel sources. Electricity can also be produced and can be used for internal and external needs. Heat from electricity production can also be used to maintain the digester temperature so that the fermentation process can be optimal. Other options are used to produce renewable natural gas (RNG). RNG can then be used for a variety of purposes both for industry and households.

Tractor with Biogas Fuel

Potential liquid waste for biogas production is from palm oil mill effluent. As the largest CPO producer in the world, Indonesia as first rank and Malaysia second rank, both of which are estimated to have more than 1500 palm oil mills, so the potential for biogas production is also very large. The processing of wastewater from oil palm mills includes large capacity, because the average palm oil mill has a capacity of 60 tons / hour FFB and produces 700 liters of liquid waste for every ton of FFB processed. The use of biogas can be used for energy sources in the palm oil mill. There are two ways that can be done on this matter, namely biogas is used to fuel the palm oil mill with existing equipment with only a few modifications, especially on the biogas burner. In this way palm kernel shells (PKS) and mesocarp fiber commonly used in energy sources can be reduced or even utilized for others.

Whereas the second method, namely biogas output is purified so that generator fuel (gas engine generator) can be used and electricity is used for the operation of the palm oil mill, while the steam needs for sterilization of palm oil mills can remain with the palm fiber and shell or biogas that is. In addition, if the biogas can be packaged in a tube (such as a 3 kg or 12 kg LPG tube) or tank, the use can be wider. Vehicles used to support the palm oil business can use biogas as fuel. Remote communities around oil palm mills who also often find electricity supply because it is very remote can use the biogas to fuel electricity generators. Various business and industrial activities can be done with the availability of electricity. This means also encouraging economic growth of the community surrounding the palm oil mill. Of course not only economic problems are stretching and developing, but also education, religion, health, and social affairs can also develop together well.