Biochar to Increase the Porosity of Damaged and Marginal Soils

Basically, porous materials will have large surface areas. The more pores, the greater the surface area of the material. Efforts to increase pores or expand the surface can be done in many ways depending on the goal. The type of pores also affects the total surface area and also the use or application of the material. For example, materials that have more micropores will have a larger surface area and have different specific uses than materials that are dominant with medium pores (mesopores) or large pores (macropores). Designing a material so that it is micropore, mesopore or macropore dominant can be done, namely by selecting raw materials and process technology, for example biochar produced from pyrolysis will produce a larger surface area compared to the initial unprocessed biomass.

In land related to use for agriculture or plant cultivation, the aspect of soil porosity or pores is an important aspect. This is mainly related to nutrient and water retention as well as soil aeration. Expanding soil pores will be very useful for improving soil quality so as to support the success of agriculture or plant cultivation. Soil that has more pore space will be able to store large amounts of water and nutrients too. Soil that has a high number of small (micropore) and medium (mesopore) pores will tend to hold water and nutrients more strongly than soil that has many large pores (macropore). And if there is evaporation or use of water by plants or a leaching process occurs in nutrients, then the large pores (macropores) left behind by the water and nutrients will follow the medium (mesopore) and  micropore.

Providing organic material in the form of compost to the soil is generally used to form more micropore spaces. The more micropore spaces that are formed, the more moisture the soil will have. Soil organic matter has more pores than soil mineral particles, which means that the surface area for absorption is also greater. Providing organic material in the form of compost, apart from increasing the number of pores or soil porosity, also reduces the volume weight. This organic material or compost is a source of energy for soil microbial activity, reduces soil volume, improves soil structure, aeration and air binding capacity. Soil with high total pores, such as clay, tends to have a low volume weight, while soil with low total pores, such as sandy soil (coarse texture), tends to have a high volume weight.

Apart from increasing total pores, adding compost also increases soil pH, namely in sandy soil and acidic soil, including entisol, ultisol and andisol and is able to reduce soil exchangeable Al. The increase in pH is due to the process of breaking down the compost. The results of this overhaul will produce basic cations which can increase the pH or release basic cations from the compost into the soil so that the soil is saturated with basic cations. The weathering or decomposition process of the compost will release alkaline cations which cause the soil pH to increase.

Soil organic C will also increase with the addition of compost and total N (nitrogen). The more organic matter added to the soil, the greater the increase in organic C in the soil. Compost from animal waste has the lowest C/N ratio compared to compost from plants. Organic materials that have a high lignin content will inhibit the speed of N mineralization and the C/N ratio will be high. In fact, further decomposition of organic matter is characterized by a low C/N ratio. Meanwhile, a high C/N ratio indicates that decomposition has not yet continued or has just started. In this process there is a decrease in carbon / C and an increase in nitrogen / N.

The need for compost on marginal land such as sandy land is also much greater, reaching almost twice as much as on ordinary or standard land. Meanwhile, the need for chemical fertilizer on marginal land is usually less than on normal/standard land. Ideally, using compost at optimal doses will be able to increase plant productivity and preserve the environment.

Unlike compost which will completely decompose, as a soil amendment, biochar can last hundreds of years in the soil. Biochar, which has a large surface area, also has many micropores which increase soil porosity, like compost. Pyrolysis conditions are important in determining the quality of biochar besides the biochar raw material itself. In rough textured soils such as sandy land, biochar will improve water and nutrient retention because its micro pores slow down its release (slow velocity). The quality of biochar is directly proportional to the efficacy of biochar treatment. A number of parameters related to the application of biochar for soil improvement/treatment are also similar to compost, including: soil carbon content and mineralization, soil micro-structural & aggregation, bioavailable nitrogen, and microbial activity & diversity. Almost all biochar is not fertilizer like compost, read more details here, so inoculation (charging) of biochar before application can be done by filling the biochar pores with water containing specific chemical elements or microbes. This will produce rapid positive effects compared to biochar alone. Apart from that, biochar is also used to reduce carbon dioxide (CO2) in the atmosphere as carbon sequestration. This is very much in line with the current problems of climate change and global warming.

Biochar is a heterogeneous substance rich in aromatic carbon and minerals. Biochar is produced from the pyrolysis process (a process where organic material is decomposed at temperatures between 350 to 1000 C with well-controlled conditions of minimal or no oxygen and is widely used for soil amendment). The carbon content for biochar must be above 50%, whereas if pyrolysis products of organic material with a carbon content of less than 50% are not included in the biochar category but are referred to as pyrogenic carbonaceous material (PCM). The organic carbon content of pyrolyzed char fluctuates between the range of 5% and 95%, depending on the raw material and temperature. process used. For example, the carbon content from pyrolysis of chicken manure is around 25%, while from wood it is around 85% and bone is less than 10%. When using mineral-rich raw materials such as sewage sludge or animal waste, the pyrolysis products will contain high ash so that the total pores are smaller.

Apart from that, biochar must also have a molar ratio of H/Corg of less than 0.7 and a molar ratio of O/Corg must be less than 0.4. The molar ratio of H/Corg is an indicator of its degree of carbonization (pyrolysis) and is therefore closely related to the stability of biochar, which is one of the most important characteristics of biochar. This ratio fluctuates depending on the type of biomass used and the conditions of the production process. A ratio value that exceeds 0.7 indicates non-pyrolytic char or inadequate pyrolysis process conditions. Meanwhile, the O/Corg ratio is also used to differentiate it from other carbon products. Specific surface area is also a measure of the quality and characteristics of biochar, and also a control value for the pyrolysis method used. Although a surface area of less than 150 m2/gram can be used in certain cases, it is preferred or preferred if it is more than 150 m2/gram.

With the characteristics above, compost and biochar as well as chemical fertilizers can be used together, even in the composting process biochar can also be added to reduce N organic released into the atmosphere. Apart from increasing the number of micro pores in the soil or increasing the total pores, the nutrients from compost and chemical fertilizers will also be released more slowly (slow release). How slow release the fertilizer can be designed depends on needs, for more details you can read here. When biochar is used properly, it can maximize harvest productivity, improve soil fertility and minimize environmental impacts. Four things need to be considered when applying biochar, namely the right source of biochar, the right location (right place), the right dose (right rate) and the right time. Not all types of soil and plants will produce increased yields from biochar applications, so it is important to know what type of soil produces increased productivity. A soil map can help to identify soil types that have the potential to provide benefits or advantages from the application of biochar. Farmers can consult with agricultural consultants or professionals in the field to help with the selection and application of biochar. 

Biochar to Improve Soil Fertility, Fuel, Industrial Raw Materials or Climate Solutions?

Currently there are still a lot of agricultural wastes (corn stalks, soybean plants, soybean shells and so on) that have not been utilized so that they pollute the environment. Utilizing these wastes so that they become useful products that provide added value is the best solution. What kind of utilization or processing is the best solution for utilizing these wastes? This of course depends on a number of influencing factors such as market readiness, availability and continuity of supply of biomass waste, especially agricultural wastes, technological readiness including technology investment, profits and business continuity, infrastructure and human resources (HR). Production of biochar or charcoal from biomass waste could be the best option. But indeed biochar or charcoal is multifunctional or can be used for a number of uses. Then the question is the use of biochar for what field gives the best results or benefits?

The biochar production is carried out using slow pyrolysis technology. With this technology biochar production can be optimal both in quality and quantity. It is different when using fast pyrolysis technology which produces biooil product or liquid product as the main product, with much less biochar product. Or if you use gasification technology where the main product is gas, so that the proportion of biochar is smaller or it can be considered as a side product, then this will also be less than optimal. These things make choosing the right technology an important thing to be able to give optimal results.

The production of biochar for agriculture has also not become a trend among farmers in Indonesia, so that much of their agricultural waste is not utilized and even pollutes the environment. Another influencing factor is the condition of the agricultural land itself. Dominant and excessive use of chemical fertilizers has damaged agricultural lands so that agricultural productivity continues to decline. And efforts to improve the soil require effort that is not easy and quick so that the fertility of the soil can be restored (recovery) and continues to be maintained for the long term. The combination of using organic materials with certain techniques needs to be done to achieve this. Biochar can also be used to make the use of organic matter more efficient, such as reducing leaching and increasing soil microbial activity. With the increased efficiency of this technique due to the use of biochar, it also minimizes input so that production costs can be further reduced. The integration of agriculture and animal husbandry is a must in order to obtain an adequate supply of organic matter, the quality is maintained and sustainable. Whereas in acid and dry soils, the use of biochar will have a more significant effect.

The use of biochar as an ingredient, especially for bbq and cooking as well as other uses, namely as a reducing agent in steel making. There are not too many uses for BBQ, this is processing or cooking food on a BBQ basis only as a hobby or only for special community segments. And there isn't much biochar for cooking either, or this is more common in Africa, while in Indonesia the option of using firewood or LPG is more common. Likewise, the need for biochar as a reducing agent in steel making is also not much. Meanwhile, the use of biochar for industrial fuels such as boiler fuel and electricity generation is almost non-existent. This is because the production process takes longer (requires a carbonization process), the conversion from biomass to biochar is small (~25%), and the price of biochar is more expensive. Wood pellets and palm kernel shells (PKS) are more of an option for these industrial fuels.

Biochar can also be used as a raw material for various industrial goods for human needs or for the substitution of materials derived from fossils (such as oil and gas) into more environmentally friendly and renewable materials. Materials such as plastic can be replaced with biochar. Particle board, which usually still uses wood waste, can also be replaced with biochar. This trend has not yet occurred, but it is predicted that soon it will become a concern and even a new trend in the industry.

Biochar for climate solutions is likely to become a trend soon. CO2 from the atmosphere is converted into biomass by plants, converted into biochar and stored (sequestration), especially in the soil. The carbon stored in the biochar will not be released into the atmosphere because biochar does not decompose for hundreds or even thousands of years or can be stored permanently. In principle, this is like storing carbon (CO2) with a conservation forest so that it becomes a carbon sink. Trees or plants will absorb CO2 from the atmosphere and be maintained in such a way as to achieve the desired CO2 uptake target then compensated with carbon credits, as well as biochar, how much carbon can be stored (sequestration) then also compensated with these carbon credits. In practice, the use of biochar will be optimal with efforts to enrich the soil on damaged or problematic soils such as post-mining soil, acid soil and diseased soil due to an overdose of chemical fertilizers. Carbon sinks with biochar are easier and cheaper than the carbon capture and storage (CCS) method with CO2 stored beneath in the earth's layers.

To reduce the temperature of the earth by reducing the concentration of greenhouse gases. To reduce 1 ppm of CO2 concentration in the atmosphere is equivalent to absorbing about 15 gigatonnes of CO2. Meanwhile, the costs needed to mitigate major climate change disasters are estimated at USD 1.6 trillion to USD 3.8 trillion each year. To reach the concentration of CO2 in the atmosphere to 350 ppm, around 70,000 biochar the size of the Giza pyramids is needed, assuming that fossil fuels are discontinued. With a volume of the Giza pyramids of 2.6 million m3 and an average biochar density of 200 kg/m3, biochar the size of the Giza pyramids weighs 520 million kg or 520 thousand tons. Huge job of course. Biochar production must grow 5000 times from its current production capacity. With biochar the size of a unit of the pyramids of Giza we need to build 4 pyramids per day (about 2 million tonnes of biochar per day) for the next 100 years and starting now.