Optimizing Wood Pellet Production from Wood Waste

The volume of wood waste from the woodworking industry in Indonesia is estimated to reach 25 million tons every year. Every wood processing will produce waste such as sawdust, wood shavings, wood chips and so on, the volume of which is around 40% of the raw materials used. However, there is still a lot of waste that has not been processed so it pollutes the environment. Meanwhile, the development of the Indonesian timber industry continues to increase due to high export demand, even though actual realization of the timber industry is still low.

It is estimated that the Indonesian wood industry can actually be optimized until its production capacity reaches 91 million cubic meters per year, but in reality in 2022 the forest products industry will only be able to produce 42.19 million cubic meters per year or around 48.7% of its optimum capacity. There are 3 factors that cause the low realization of the wood industry, namely, efficiency of the wood industry, problems related to raw materials and market availability.

The low efficiency of the woodworking industry is due to the use of old machines or traditional methods for production. Meanwhile, problems related to raw materials are caused by the reduction in forest areas due to the large amount of development that causes forest land to change its function. Efforts to maintain a stable and sustainable supply of wood raw materials need to be made, including land rehabilitation programs and coaching for community forest farmers. National mapping of wood potential also needs to be carried out so that industry can obtain information regarding the supply of raw materials needed. Market availability is also an important factor in the development of the timber industry, so the ability to access information and identify market aspects, both domestic and international, is needed.

As the wood industry increases, wood waste also increases. An environmentally conscious industry certainly pays great attention to waste issues so that ideally it can achieve zero waste. These wastes are raw materials for wood pellets. The need for wood pellets continues to increase in line with the global decarbonization trend. Just as the woodworking industry requires consistency to maintain its products, so does wood pellet production. The consistency of the wood pellet raw material mixture is the key to the quality of wood pellets, including making production optimal.

In large woodworking factories, wood pellet production can be carried out simply by using its own waste, so that apart from solving the waste problem according to the zero waste concept, it can also be used as a new business development. Meanwhile, in the small - medium woodworking industry, because there is insufficient wood waste, some wood waste as raw material for wood pellets needs to be sourced from other places. A wood pellet factory can also be made independently, namely with raw materials that come 100% from other people's woodworking factory waste, meaning that the wood pellet factory is not owned by a wood processing industry. So basically a wood pellet factory is a factory or installation for processing wood waste that produces products with high selling value and is in line with the global decarbonization trend.

Export-Oriented Large Capacity Wood Pellet Production

Availability of raw materials and market control are the two absolute main things that must be fulfilled so that the wood pellet production business can be sustainable. Investing in expensive equipment will be useless if the two things mentioned above are not met. In large capacity wood pellet production, the quality of the production equipment used is very important. The production goal of achieving large capacity will be achieved if it is carried out with an efficient and safe production process so that production costs are low. Production equipment that is capable of working non-stop 24 hours, easy operation and maintenance with good performance is vital. Regarding raw materials, apart from continuous availability, there are 2 important things that need to be considered, namely the consistency of raw materials and cheap logistics to the location of the wood pellet factory.

Mapping the potential of raw materials needs to be done well, as well as the wood pellet market. Wood pellet raw materials from one type of wood (single material) are certainly easier than mixed raw materials from several types of wood. This is related to the composition of the mixture, which of course is not a problem if the raw material is from one type of wood (single material) which is homogeneous. To strive for homogeneous raw materials, this can be done by creating energy plantations, while mixed raw materials can be taken from several wood processing sources such as sawmills and so on. Energy plantations that can be multifunctional so that they provide many benefits. This can be done by maintaining a balance between wood productivity for wood pellet production, environmental functions in the form of maintaining erosion and groundwater, and the volume of wood harvested must not exceed the growth rate or be at least the same (carbon balance) and the use of by-products for additional revenue such as utilization leaves for animal feed and honey from beekeeping.

 

Meanwhile, from a market aspect, a number of requirements also need to be met so that sustainable transactions occur. Apart from technical factors in the form of wood pellet specifications and production volume, non-technical factors such as sources of raw materials related to environmental sustainability are also often required nowadays. Users of wood pellets abroad, especially power plants, are in decarbonization efforts through cofiring programs with coal. Sustainable decarbonization efforts usually require environmental certificates such as FSC regarding the source of the raw materials used. This is to prove that the renewable fuel chain, especially wood pellets, indeed complies with mutually acceptable environmental sustainability standards. There are certain countries that impose long contracts for the purchase or procurement of their wood pellets, but there are also those that choose short-term contracts. The typical buyer or market for wood pellets also needs to be given special attention.

Green Economy in the Cement Industry Part 6: Clinker Substitution in Cement Plants

Substituting clinker with additives or SCM (Supplementary Cementious Material) plays a major role in efforts to reduce CO2 emissions in cement plants. This clinker substitution is ranked second after carbon capture or CCS (Carbon Capture and Storage) in efforts to reduce CO2 emissions or decarbonization in the cement industry. This is because the largest CO2 emissions in cement plants are not from combustion or related to fuel but in the calcination process. CCS technology is still expensive so its implementation still faces many obstacles, but clinker substitution is easier to do, so many cement plants are already doing it. 

In the cement industry, all fuel use and around 60% of electricity use is used for clinker production starting from grinding raw materials, fuel preparation and cement kilns. The higher the clinker to cement ratio, the higher the electricity and fuel used for each ton of cement produced. The clinker to cement ratio can be reduced if less clinker is used in cement production or more additional materials or SCM are added to the clinker. This also means that substituting clinker with SCM can significantly reduce energy use (electricity and fuel) for each ton of cement produced. 

China currently has the lowest clinker to cement ratio in the world, namely 0.58, while a number of areas in other countries have the highest ratio, up to 0.9. It can also be understood that China uses the highest portion of SCM compared to countries in the world. The most commonly used SCMs today are fly ash, ground granulated blast-furnace slag (GGBFS) and ground limestone. Meanwhile, other SCMs such as pozzolan and calcined clay have the potential to be used in the future.

Fly ash comes from by-products or waste from coal-fired power plants. Decarbonization of coal power plants is also continuing to be carried out, namely by cofiring coal with biomass, but this is being done in stages so that fly ash production will still be large for a while. Fly ash from coal-fired power plant waste is very useful in cement production because it reduces the clinker to cement ratio, thereby reducing energy requirements for cement production or in other words reducing the carbon footprint of cement products. Meanwhile, GGBFS comes from iron and steel plant waste. Not all iron and steel plants produce GGBFS waste, this is because it depends on the type of furnace used. Only plants that use blast furnaces - basic oxygen furnaces (BF - BOF) can produce GGBFS, while those that use electric arc furnaces (EAF) cannot. Around 70% of iron and steel plants in the world currently use the BF – BOF process so as to produce quite a lot of GGBFS, even in China more than 90% use this BF – BOF process. Decarbonization in the iron and steel industry is marked by the switch from BF – BOF to EAF which results in the availability of GGBFS. However, the process is running slowly and gradually, so that for a while the amount of GGBFS will be available and can reduce the carbon footprint of cement production.

The use of fly ash in cement production is usually limited to 25-35% for technical performance reasons. Meanwhile, GGBFS can be used in larger portions than fly ash or other SCM. Even European standards allow the use of GGBFS up to 95% but in practice it is lower. Other SCMs commonly used are pozzolan and calcined clay. Pozzolan comes from mining, namely from deposits in nature. Pozzolan requires drying and grinding before being used in cement production. The electricity used for crushing (grinding) pozzolan is also almost the same as crushing clinker. Calcined clay can also be used as a substitute for clinker. The initial use of calcined clay with a higher portion causes a decrease in the compressive strength of the cement product produced. However, further developments using a combination or mixture of calcined clay with limestone powder have the potential to substitute up to 50% clinker without affecting the quality of the cement. Calcined clay is produced from the clay calcination process which requires energy, but the energy required is much less than the energy for clinker production. It is predicted that in 2050 by the IEA (International Energy Agency) / WBCSD (World Business Council for Sustainable Development) cement production with the above combination of materials will reach more than 25% worldwide.

It turns out that the use of SCM is not only a substitute for clinker in cement production but also in concrete production. The use of SCM in concrete production is also no less than a substitute for clinker, even in the United States SCM is mostly added during concrete production and not during cement production. A study in the United States estimated that only 5% of SCM was added to cement production and around 13% to concrete production. But basically the addition of SCM to both cement production and concrete production has reduced the carbon footprint or is in line with decarbonization. The problem is that the lack of education regarding the benefits of SCM, especially in concrete production, is a barrier to increasing the use of SCM. Other factors such as the availability of SCM, price and its relation to cement and building quality are also similar barriers. The creation of new standards and codes related to increasing the use of blended cement with SCM and concrete production needs to be developed to transform the current market.

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.