Biochar to Increase Biogas Production

Charcoal (biochar) is the raw material for the production of activated carbon. The production of activated charcoal itself goes through two main processes, namely carbonization (pyrolysis) and activation. The surface area of charcoal (biochar) is also smaller than that of activated carbon, but larger than the raw biomass. The carbonization process increases the surface area of the raw biomass. The ratio of surface area between raw biomass, charcoal and activated charcoal is approximately 25 m2 / gram, 200 m2 / gram, 2000 m2 / gram. The larger the surface area of the biomass material that is inserted into the biogas reactor, the greater the penetration of bacteria into the substrate so that the fermentation process that occurs is more perfect so that biogas production will increase. Biochar itself does not participate in fermentation because the main component is stable carbon, while hemicellulose, cellulose and lignin have been decomposed during the carbonization process.

Another example is the addition of biomass briquettes to the biogas reactor, briquetting processs with high pressure and heat also open pores or expand the surface of the biomass, so that biogas production also increases, for more details, read here. The addition of biomass briquettes to the biogas reactor will also increase the C / N ratio, even biochar and activated charcoal have high carbon (C) content.

Charcoal (biochar) has been widely used in the agricultural world to repair damaged soil / soil amendment and thus increase fertility. Good soil fertility will also increase agricultural production. The biochar becomes a home for soil microbes, so that organic materials or compost will break down more completely and be absorbed by plants more as plant nutrients. The charcoal (biochar) pores are the home for these microbes. The more pores, the more microbes will inhabit the biochar as their “house”. The same principle applies to the biogas unit. Another bonus of using biochar is that it absorbs CO2 from the atmosphere, thereby contributing to lowering the greenhouse gases that cause climate change and global warming.

Research in Germany shows that adding 5% biochar to a biogas reactor increases methane production by 5% - based on the dry matter of biochar to the substrate. But when the amount of biochar became 10%, it turned out that no more methane was added. This shows that the optimum condition for adding biochar is the amount of 5%. The microbes in the biochar increase the volume of microbes in the reactor so that the production of biogas or especially methane also increases up to 5%. Biochar itself is not decomposed in the fermentation process. 

Meanwhile, the addition of biomass briquettes per 1 tonne of briquettes will increase biogas production by 400 Nm3. This is because in the biomass briquettes, both cellulose, hemicellulose and lignin have not been decomposed, thus adding to the substrate in the biogas reactor. Whereas in biochar, both cellulose, hemicellulose and lignin have been decomposed during the thermal carbonization process, so there is practically no additional substrate, but only microbial addition occurs in the biochar pores.

The important thing about the addition of biochar is that the compost or digestate produced is of better quality with the addition of the biochar. Biochar will make the compost which is produced as a slow release organic fertilizer. This further encourages biochar production, especially for palm oil companies that care about environmental issues and even strive for zero waste conditions.

Palm oil mills have the potential to apply biogas and biochar units. Solid wastes such as empty bunches and mesocarp fiber can be used for biochar production. Palm oil mills can even replace the furnace in the boiler with a gasifier or pyrolyser. This becomes more profitable because in addition to heat energy being used for production of steam which is used for power generation and sterilization of fresh fruit, biochar will also be produced. The biochar produced is then used to increase biogas production and improve the quality of the compost, as well as a fertilizer mixture in palm oil plantations. And even the potential use of biochar to save fertilizer on large palm oil plantations, for more details can be read here.

Estimated Increase in POME Biogas Production in Indonesia and Malaysia with the Addition of Biomass Briquettes

 

The important thing that needs to be done to implement a research in a commercial unit is the technical and economic side. A research product that has been tested technically needs to be evaluated on the economic side. This is because in commercial units, the economic aspect is the main consideration for the implementation of a certain technology. A technology implemented with the intention of improving the performance of these commercial units but not providing economic benefits generally will not attract many. Likewise, vice versa. How much economic benefit can be obtained from implementing this technology? Is it worth the effort? These two questions will be considered next.

In the biogas unit (mostly for electricity production) the above rules also apply. And especially the biogas unit in Indonesia and Malaysia as the largest CPO (crude palm oil) producer in the world, the POME biogas unit or palm oil mill liquid waste has been built as a means of overcoming the problem of liquid waste and also energy production, especially electricity. Tens or even hundreds of POME biogas units have been built in Indonesia and Malaysia, but that number is not yet comparable to the number of palm oil mills in Indonesia and Malaysia which has reached thousands. And more specifically, the number of POME biogas units in Indonesia is less or a smaller percentage compared to palm oil mills compared to Malaysia. Why did this happen? For more details, please read here.

And because the commercial end product of the commercial biogas unit is electricity, the price of electricity will greatly affect the operation of the biogas unit. Research conducted at Aarhus University in Denmark shows that biomass briquettes can significantly increase biogas production, that is, every 1 tonne of straw briquettes added has increased biogas production by an average of 400 cubic meters. With a biogas caloric value of around 4500 kcal / m3, each tonne of addition of straw briquettes will increase calories by 1,800,000 kcal in the form of biogas. for more details, please read here. In the case of POME biogas, if empty fruit bunches (EFB) are used as raw material for briquettes, it could be an increase in the biogas product produced. This is because the EFB have undergone a sterilization process (steamming) so that the biomass pores are more open so that the surface area is larger. The briquetting of the EFB will also further expand the surface of the biomass so that the anaerobic fermentation process is more perfect and the biogas product increases.

Assuming the electricity price per kwh in Malaysia from biogas is 0.49 RM (IDR 1,715) and IDR 1000 in Indonesia, with the increase in biogas produced above, Malaysia will be more attractive and profitable. However, this increase in biogas production has also yielded attractive advantages when applied, both in Indonesia and Malaysia. The estimate assuming a biogas reactor capacity of 150,000 tonnes and with the addition of 15,000 tonnes of biomass briquettes (maximum 10% of the reactor volume) has resulted in profits of nearly 27 billion rupiah/Rp (application in Indonesia) and 14 million Malaysian ringgit/RM (application in Malaysia). Under these conditions, it is actually very interesting to implement this research on POME biogas power plants in Indonesia and Malaysia. Apart from reducing solid waste from the palm oil industry, increasing biogas production which is proportional to electricity production will provide attractive benefits for the palm oil industry.

Increasing Biogas Production With Biomass Briquettes

For example, activated carbon which has much more pores than ordinary charcoal, or one spoon of activated charcoal is estimated to have a surface area like the area of ​​a football field. With this surface area, activated carbon can adsorb much more molecules than ordinary charcoal. That is what makes activated carbon used by many industries, for more details, you can read it here. The activation process is the process of creating or opening the pores of charcoal so that it has a large surface area. Likewise with the biomass briquetting process, due to the strong pressure and high temperature of the briquetting process with a mechanical press, the micro pores of the biomass will open. The opening of the biomass pores will increase its absorption power. It turns out that according to research at Aarhus University Denmark, the use of biomass briquettes, especially straw briquettes, has been able to significantly increase biogas production. Every 1 tonne of straw briquettes added has increased the biogas production by an average of 400 cubic meters. With a biogas caloric value of around 4500 kcal / m3, each tonne of addition of straw briquettes will increase calories by 1,800,000 kcal in the form of biogas. Meanwhile, every 1 m3 of POME will produce about 25 m3 of biogas.

The research was conducted on a continous stirred tank reactor (CSTR) biogas type so that the effort to maximize the substrate mixture of biogas was carried out mechanically. CSTR for biogas production is still rare in Indonesia and the Southeast Asia region today, but is common in Europe. The addition of briquettes to the biogas reactor also means adding organic material as raw material for biogas production. But with this form of briquette which has the ability to absorb much more water or 10 times that of bulk straw without be briquetted, which causes microbes to penetrate far more through the micro pores of the straw briquettes, as a result the fermentation process is more perfect. Based on these experiments, the biogas production reached the optimum level at the addition of 10% straw briquettes to the reactor volume. The addition of straw briquettes of up to 10% apparently did not interfere with the performance of the stirrer motor and the straw briquettes because the micro pores absorbed water optimally and did not create floating material that covered the surface of the reactor. 

For biogas factories in Indonesia, especially Southeast Asia in general, especially those that use CSTR for biogas production, of course the above can be a reference and guide for trials to increase biogas production by adding biomass briquettes. In the above case, the straw used in Denmark uses straw from the wheat plant because it is abundantly available there, while in Indonesia and Southeast Asia, rice straw is widely available. The properties of wheat straw and rice straw are so similar that it is also predicted that they will produce almost the same volume of biogas. But if the biogas unit is for example in palm oil mills, biomass sources such as mesocarp fiber, empty bunches and palm leaves can be used as raw material for the briquettes. The biogas unit commonly used in palm oil mills in Indonesia and Southeast Asia using palm oil mill effluent as raw material is a covered lagoon which is not equipped with a mixer. For this type of reactor, one of the efforts to increase biogas production is by making the operating conditions thermophilic. The heat from the biogas power plant can be used to reach this temperature. Can biomass briquettes increase biogas production in covered lagoon reactors? The answer still needs further research.

Why Do Most Palm Oil Mills Not Have Biogas?

Palm oil plantations are the largest plantations in Indonesia with an estimated area of ​​more than 12 million hectares or are the largest palm oil plantations in the world with CPO production reaching more than 40 million tons / year and an estimated more than 1,000 palm oil mills. Malaysia is second ranked for the area of ​​palm oil plantations following CPO production. Biogas energy is the potential energy from the palm oil mill wastewater treatment or POME (palm oil mill effluent). Around 0.7 m3 of liquid waste is produced by the palm oil mill per tonne of FFB (fresh fruit bunch) treated. Biogas usually consists of 50-75% methane (CH4), 25-45% carbon dioxide (CO2), and a number of other gases. If liquid waste management is not controlled, the methane in biogas is released directly into the atmosphere. As a greenhouse gas (GHG), methane has an effect 21 times greater than CO2. Almost all biogas production is used for electricity production. In addition to electricity production, it is environmentally friendly and is also a means of treating waste and preventing climate change. But why are there so few palm oil mills in Indonesia or it is estimated that less than 10% have these biogas units? There are a number of analyzes of why this happens.

A. The prospect of biogas is less attractive

Although it has an abundant source of raw materials in the form of liquid waste (POME), but when electricity products are only bought cheaply, it is not attractive, because for the procurement and installation of biogas units and power plants requires huge costs. The payback period is also getting longer even though operational costs have also increased over time. In addition, the BOT mechanism (built, operated, transferred) after a certain period of time also makes palm oil entrepreneurs less interested.

B. Lack of vision for business development

Electrical energy is energy that is very flexible or easily transformed into other forms of energy. So the availability of electrical energy should be able to encourage the development of other businesses. But with the lack of vision in the business development, the motivation for electricity production from the biogas unit is also weak. A number of businesses can be built if electricity is available, for example a kernel crushing plant (KCP). Palm oil mills are currently only producing CPO, while the kernel or palm kernel which produces palm kernel oil (PKO) is only sold to other mills. EFB or fiber pellets can also be produced if there is enough electricity. Mechanical devices for the production of pellets require adequate and stable electricity supply. Besides CPO derivative plants such as oleochemicals can also be built if electricity supply is available.

C. Unclear environmental regulation

Weak environmental regulations will also hamper the development of biogas units. Untreated liquid wastes will potentially produce dangerous GHGs, especially methane. If this environmental hazard becomes the concern of all parties and produces a number of regulations, the potential for environmental pollution can be reduced and the biogas unit can be a surefire solution to overcome the problem.

Then how is the solution so that palm oil mills protect environmental problems and at the same time provide economic benefits? The biogas unit is still being built and operated with its electricity output for the development of a number of industries mentioned above. Another option that can be done is to create a biogas unit but not for direct electricity production, but for heat production. The heat is used for palm mill boiler operations. With heat coming from biogas, the palm kernel shell (PKS) can be sold or exported.

  For palm oil mills that need biogas units or biogas gas engines (generators), whether new or second / used or only repair and maintenance / service, please send an email to: eko.sbs@gmail.com