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.

EFB Biochar and Fertilizer Savings in Palm Oil Plantations

High palm oil plantation productivity and high oil yield has always been a goal in the palm oil business. The nutrient estimates needed to produce 25 tons of FFB / ha / year were 192 N, 11 P, 209 K, 36 Mg, and 71 Ca in kg / ha / year. With the production of 25 tons of FFB / ha / year palm oil or CPO crude will produce around 6.5 tons (25% of FFB). Analogy in the field of animal husbandry where the feed component holds 75% of production costs or is the highest cost component, as well as fertilizer, especially in palm oil plantations. Fertilizer is the most expensive cost or 60% of total maintenance costs. To achieve this productivity, the calculation practically of the need is more or less as follows: an afdeling with an area of ​​1,000 hectares with 1 hectare consisting of 143 trees, so there are 143,000 trees of palm oil. If the dose per tree is 2.5 kg, then the fertilizer needs are 357,500 kg (357.5 tons), with the price of non-subsidized chemical fertilizers for example Rp 10,000 / kg, the cost incurred is 3,575,000,000 (Rp. 3,575 billion or US$ 238,333). If an area of ​​10,000 hectares means fertilizer needs of Rp. 35.75 billion (US$ 2,383,33), whereas if the oil palm plantation is 20,000 hectares, it will reach Rp. 71.50 billion (US$ 4,766,667). Of course an amount that is not small.

The question is what efforts can be made to reduce fertilizer costs but increase palm productivity. One contradictory thing seems to be because it reduces the supply of fertilizer but expects high productivity. This is where we need to examine and explore the facts that occur in the field. With a tropical climate and high rainfall, it makes large leached fertilizers. A condition, for example in hilly and bumpy areas, when the rain falls, the fertilizer that is washed is very large, even in vain fertilization is done because it is not absorbed by the palm trees as the target. The high level of leaching from the use of fertilizers by rainwater makes only available a small amount of available fertilizer in real terms or a number of analyzes said averaging only 50%. With the available fertilizers there are only a few that are also automatically absorbed by the palm trees. When for example washing (leaching) can be reduced by only 30%, it means that the fertilizer that is still available becomes 70%, so that the fertilizer is absorbed more and more and the productivity of the palm oil fruit also increases.

The initial stage that can be done is the cost of the same fertilizer but the productivity of the palm oil fruit can increase up to for example 30%. Furthermore, if this can be achieved, fertilizer consumption will be reduced for example up to 30% but palm oil productivity can be maintained at that level. This is possible when biochar has become a microbial colony and the quality of the soil increases so that uptake of fertilizer is maximal. Biochar is one of the media that can be used for this. An empty fruit bunch that is widely available in palm oil mills and is generally not utilized as a raw material for biochar production. A palm oil mill with a production capacity of 60 tons / hour FFB will produce EFB 13.2 tons / hour so that if the palm oil mill operates 20 hours / day the EFB produced 264 tons / day. The production of biochar with pyrolysis can also produce liquid smoke which can also be used as fertilizer.

Why can biochar be used to increase palm oil productivity and even reduce fertilizer consumption? This is because biochar with its pores with a surface area of ​​about 200 m2 / gram can hold the fertilizer from washing, maintain moisture and many soil microbes that can live in these pores thus improving the physical and chemical properties of the soil. Biochar can last up to hundreds of years in the soil so it does not need to be added every year when the amount is sufficient. Biochar implementation can be started from small scale to massive scale. To process empty fruit bunches (EFB)  in the palm oil mill into biochar, a continuous pyrolysis equiment is needed, to be more clearly read here. To monitor the effectiveness of biochar on oil palm plantations today can use internet technology or IoT (Internet of Things) and for more details can be read here and here.