Sugarcane is one of the most promising agricultural sources of biomass energy in the world. It is the most appropriate agricultural energy crop in most sugarcane producing countries due to its resistance to cyclonic winds, drought, pests and diseases, and its geographically widespread cultivation. Due to its high energy-to-volume ratio, it is considered one of nature’s most effective storage devices for solar energy and the most economically significant energy crop.
The climatic and physiological factors that limit its cultivation to tropical and sub-tropical regions have resulted in its concentration in developing countries, and this, in turn, gives these countries a particular role in the world’s transition to sustainable use of natural resources.
According to the International Sugar Organization (ISO), Sugarcane is a highly efficient converter of solar energy, and has the highest energy-to-volume ratio among energy crops. Indeed, it gives the highest annual yield of biomass of all species. Roughly, 1 ton of Sugarcane biomass-based on Bagasse, foliage and ethanol output – has an energy content equivalent to one barrel of crude oil.
Sugarcane produces mainly two types of biomass, Cane Trash and Bagasse. Cane Trash is the field residue remaining after harvesting the Cane stalk and Bagasse is the milling by-product which remains after extracting sugar from the stalk. The potential energy value of these residues has traditionally been ignored by policy-makers and masses in developing countries. However, with rising fossil fuel prices and dwindling firewood supplies, this material is increasingly viewed as a valuable renewable energy resource.
Sugar mills have been using Bagasse to generate steam and electricity for internal plant requirements while Cane Trash remains underutilized to a great extent. Cane Trash and Bagasse are produced during the harvesting and milling process of Sugarcane which normally lasts 6 to 7 months.
Around the world, a portion of the Cane Trash is collected for sale to feed mills, while freshly cut green tops are sometimes collected for farm animals. In most cases, however, the residues are burned or left in the fields to decompose. Cane Trash, consisting of Sugarcane tops and leaves can potentially be converted into around 1kWh/kg, but is mostly burned in the field due to its bulkiness and its related high cost for collection and transportation.
On the other hand, Bagasse has been traditionally used as a fuel in the Sugar mill itself, to produce steam for the process and electricity for its own use. In general, for every ton of Sugarcane processed in the mill, around 190 kg Bagasse is produced.
Low pressure boilers and low efficiency steam turbines are commonly used in developing countries. It would be a good business proposition to upgrade the present cogeneration systems to highly efficient, high pressure systems with higher capacities to ensure utilization of surplus Bagasse.
Biomass energy has rapidly become a vital part of the global renewable energy mix and account for an ever-growing share of electric capacity added worldwide. Renewable energy supplies around one-fifth of the final energy consumption worldwide, counting traditional biomass, large hydropower, and “new” renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels).
Traditional biomass, primarily for cooking and heating, represents about 13 percent and is growing slowly or even declining in some regions as biomass is used more efficiently or replaced by alternative energy forms. Some of the recent predictions suggest that biomass energy is likely to make up one third of the total world energy mix by 2050. Infact, biofuel provides around 3% of the world’s fuel for transport.
Biomass energy resources are readily available in rural and urban areas of all countries. Biomass-based industries can foster rural development, provide employment opportunities and promote biomass re-growth through sustainable land management practices.
The negative aspects of traditional biomass utilization in developing countries can be mitigated by promotion of modern waste-to-energy technologies which provide solid, liquid and gaseous fuels as well as electricity. Biomass wastes encompass a wide array of materials derived from agricultural, agro-industrial, and timber residues, as well as municipal and industrial wastes.
The most common technique for producing both heat and electrical energy from biomass wastes is direct combustion. Thermal efficiencies as high as 80 – 90% can be achieved by advanced gasification technology with greatly reduced atmospheric emissions.
Combined heat and power (CHP) systems, ranging from small-scale technology to large grid-connected facilities, provide significantly higher efficiencies than systems that only generate electricity. Biochemical processes, like anaerobic digestion and sanitary landfills, can also produce clean energy in the form of biogas and producer gas which can be converted to power and heat using a gas engine.
Advantages of Biomass Energy
Biomass energy systems offer significant possibilities for reducing greenhouse gas emissions due to their immense potential to replace fossil fuels in energy production. Biomass reduces emissions and enhances carbon sequestration since short-rotation crops or forests established on abandoned agricultural land accumulate carbon in the soil.
Bioenergy usually provides an irreversible mitigation effect by reducing carbon dioxide at source, but it may emit more carbon per unit of energy than fossil fuels unless biomass fuels are produced unsustainably.
Biomass can play a major role in reducing the reliance on fossil fuels by making use of thermochemical conversion technologies. In addition, the increased utilization of biomass-based fuels will be instrumental in safeguarding the environment, generation of new job opportunities, sustainable development and health improvements in rural areas.
The development of efficient biomass handling technology, improvement of agro-forestry systems and establishment of small and large-scale biomass-based power plants can play a major role in rural development and sustainable utilization of biomass. Biomass energy could also aid in modernizing the agricultural economy.
Consistent and reliable supply of biomass is crucial for any biomass project
When compared with wind and solar energy, biomass power plants are able to provide crucial, reliable baseload generation. Biomass plants provide fuel diversity, which protects communities from volatile fossil fuels. Since biomass energy uses domestically-produced fuels, biomass power greatly reduces our dependence on foreign energy sources and increases national energy security.
A large amount of energy is expended in the cultivation and processing of crops like sugarcane, coconut, and rice which can met by utilizing energy-rich residues for electricity production.
The integration of biomass-fueled gasifiers in coal-fired power stations would be advantageous in terms of improved flexibility in response to fluctuations in biomass availability and lower investment costs. The growth of the bioenergy industry can also be achieved by laying more stress on green power marketing.
Lignocellulosic biomass consists of a variety of materials with distinctive physical and chemical characteristics. It is the non-starch based fibrous part of plant material.
Lignocellulose is a generic term for describing the main constituents in most plants, namely cellulose, hemicelluloses, and lignin. Lignocellulose is a complex matrix, comprising many different polysaccharides, phenolic polymers and proteins. Cellulose, the major component of cell walls of land plants, is a glucan polysaccharide containing large reservoirs of energy that provide real potential for conversion into biofuels.
First-generation biofuels (produced primarily from food crops such as grains, sugar beet and oil seeds) are limited in their ability to achieve targets for oil-product substitution, climate change mitigation, and economic growth. Their sustainable production is under scanner, as is the possibility of creating undue competition for land and water used for food and fibre production.
The cumulative impacts of these concerns have increased the interest in developing biofuels produced from non-food biomass. Feedstocks from lignocellulosic materials include cereal straw, bagasse, forest residues, and purpose-grown energy crops such as vegetative grasses and short rotation forests. These second-generation biofuels could avoid many of the concerns facing first-generation biofuels and potentially offer greater cost reduction potential in the longer term.
The largest potential feedstock for biofuels is lignocellulosic biomass, which includes materials such as agricultural residues (corn stover, crop straws and bagasse), herbaceous crops (alfalfa, switchgrass), short rotation woody crops, forestry residues, waste paper and other wastes (municipal and industrial). Bioethanol production from these feedstocks could be an attractive alternative for disposal of these residues.
Importantly, lignocellulosic biomass resources do not interfere with food security. Moreover, bioethanol is very important for both rural and urban areas in terms of energy security reason, environmental concern, employment opportunities, agricultural development, foreign exchange saving, socioeconomic issues etc.
Lignocellulosic biomass consists mainly of lignin and the polysaccharides cellulose and hemicellulose. Compared with the production of ethanol from first-generation feedstocks, the use of lignocellulosic biomass is more complicated because the polysaccharides are more stable and the pentose sugars are not readily fermentable by Saccharomyces cerevisiae.
In order to convert lignocellulosic biomass to biofuels the polysaccharides must first be hydrolysed, or broken down, into simple sugars using either acid or enzymes. Several biotechnology-based approaches are being used to overcome such problems, including the development of strains of Saccharomyces cerevisiae that can ferment pentose sugars, the use of alternative yeast species that naturally ferment pentose sugars, and the engineering of enzymes that are able to break down cellulose and hemicellulose into simple sugars.
Lignocellulosic biomass processing pilot plants have been established in the EU, in Denmark, Spain and Sweden. The world’s largest demonstration facility of lignocellulose ethanol (from wheat, barley straw and corn stover), with a capacity of 2.5 Ml, was first established by Iogen Corporation in Ottawa, Canada. Many other processing facilities are now in operation or planning throughout the world.
Economically, lignocellulosic biomass has an advantage over other agriculturally important biofuels feedstock such as corn starch, soybeans, and sugar cane, because it can be produced quickly and at significantly lower cost than food crops.
Lignocellulosic biomass is an important component of the major food crops; it is the non-edible portion of the plant, which is currently underutilized, but could be used for biofuel production. In short, biofuels from lignocellulosic biomass holds the key to supplying society’s basic needs without impacting the nation’s food supply.
The medical and recreational cannabis industries are continuously growing and with more and more countries deciding to legalise, many are turning to growing their own cannabis.
However, one downside can be the energy it takes to power the lighting, heating, pumps and ventilation needed to successfully grow a cannabis plant. In fact, did you know that on average, producing one pound of cannabis requires about 2,000 kWh; the same amount of which the average household will use in two and a half months!
Luckily, in the article below, we have put together a range of methods you can use to save energy, money while growing cannabis. This has been written in collaboration with 2 Fast 4 Buds, leading providers of autoflowering cannabis seeds.
Use LED Lights
LED lights are a much more energy efficient option, compared to other types of lighting. Therefore, if you are looking to cut down on your energy usage and therefore costs, they’re a great choice to make!
They won’t produce as much heat as other lights and will also cool down much quicker, which goes even further in reducing your energy costs. What’s more, more often than not LEDs will have a light spectrum which is perfect for your plants needs.
Overall, choosing LED grow lights means higher efficiency because less power is converted into heat and into a light spectrum of which your plant doesn’t fully appreciate.
Adjust the Size of your Grow to Your Needs
By adjusting how many cannabis plants you are growing to how much you actually need, you can make a big impact on your energy costs. In fact, this is by far one of the most effective ways to reduce your energy consumption.
For example, if you are using around 30g of cannabis a month, one single autoflower plant can produce this amount in its life cycle of 8 weeks. Therefore, by having four plants, you can ensure that you’re well stocked.
Try to perfectly match how much energy you use on your plants with the amount you need.
Improve Your Insulation
If the space in which you are growing your cannabis isn’t properly insulated, then you will be wasting a huge amount of energy. This especially applies if you are using a heater or an air conditioner to help keep the space at the right temperature.
To ensure that your space is properly insulated, you want to use styrofoam wall panelling to insulate doors and windows and ensure that any piping in the room is properly insulated. This will help to ensure that you aren’t unnecessarily running your air conditioner or heater.
Optimise Your Climate Control
It’s also important to remember that you don’t need to constantly run your heaters, coolers and (de)humidifiers on full blast. In fact, many professional greenhouse growers will choose to measure a value known vapour pressure deficit or VPD. VPD will indicate the difference between the amount of moisture in the air and how much moisture the air can hold when it is saturated. This will then allow you to achieve the optimal climate for your plants, benefiting their health and also your energy usage.
You could also consider an integrated climate control system. Whilst this involves much more than just having a heater or air conditioner, an ICCS will intelligently control all of your growing equipment. For example, the system could temporarily switch off your exhausts to ensure that you aren’t wasting CO2 unnecessarily.
Sometimes, however simple methods prevail when optimising the climate for your plants. You could just run an ordinary standing fan or open a window or door to let fresh air in, and this could be enough for you to save on additional cooling methods.
Monitor Your Energy Consumption
If you are looking to cut down on the amount of energy you are using to grow cannabis, it is important to keep track of exactly how much energy you are using. From this you will be able to formulate a plan to control consumption and actually make adequate changes.
Establishing energy-spending targets of which you plan to achieve are a great starting point. However before you do this, make sure you know how much your energy costs per KW/h and how much energy each individual piece of equipment uses. Not knowing this will mean that the whole process will essentially be a guessing game, making saving energy much more difficult.
Take a look at your energy consumption in previous months and see whether you can improve on this. Even if you are making small changes, these can go a long way.
Once you understand how much energy you are using and how much is essentially going to waste, then you can make appropriate changes. This can include switching your grow lights for LEDs, reducing your light hours, installing climate control and so on.
After making these changes, make sure to check as to whether you’re actually hitting your previously set goals and therefore whether your energy-saving tactics are actually working. IF you find that improvements are small, think of it as an opportunity to make more changes, whether that’s making more tweaks or consulting an expert.
Saving More Water
Being energy efficient isn’t just about cutting down how much electricity you use, it’s also about lowering your overall environmental footprint. Another great way to do this is by saving water.
Make sure to water your plants only when they need it. Lifting up your pots can help you to determine how much water is in there. Make sure to only water the plants when the pots are light. Even better, set up specialised sensors to do this for you!
Whilst hand watering may not seem hard, overwatering is an incredibly easy mistake to make. Using an irrigation system can ensure that water waste is greatly reduced and benefit the overall health of your cannabis plants.
Another great way to save water is by stopping ‘drain-to-water’ watering and choosing to grow your plants hydroponically. Hydroponic systems use tanks to recirculate water and therefore nutrients, resulting in significant water savings. These systems are also much more environmentally friendly as they don’t waste large quantities of water and nutrients.
When growing cannabis, you want to ensure that all of your equipment is working at its best and the only way to ensure this is by performing regular maintenance.
If you own either an irrigation or hydroponic system, you want to ensure that you are cleaning it and replacing filters and valves regularly. Your system will also require a cleaning ‘flush’ once in a while.
Likewise, you will want to keep a grow room as clean as possible, to reduce the likelihood of equipment failures.
If it is available to you, moving your plants outdoors could effectively remove the costs of operating an indoor growing system.
If you want to go a step further, investing in a greenhouse could be well worth it. A greenhouse will provide both you and your plants with all of the benefits of growing indoors, along with those of growing outdoors!
No matter how you do it, it is actually fairly easy to make your cannabis growing system more energy efficient. By no means will you have to sacrifice on the quality of your plant and you’ll benefit from a lower energy bill at the end of the day!
Coconuts are produced in 92 countries worldwide on about more than 10 million hectares. Indonesia, Philippines and India account for almost 75% of world coconut production with Indonesia being the world’s largest coconut producer. A coconut plantation is analogous to energy crop plantations, however coconut plantations are a source of wide variety of products, in addition to energy. The current world production of coconuts has the potential to produce electricity, heat, fiberboards, organic fertilizer, animal feeds, fuel additives for cleaner emissions, eco-friendly cutlery, health drinks, etc.
The coconut fruit yields 40 % coconut husks containing 30 % fiber, with dust making up the rest. The chemical composition of coconut husks consists of cellulose, lignin, pyroligneous acid, gas, charcoal, tar, tannin, and potassium. Coconut dust has high lignin and cellulose content. The materials contained in the casing of coco dusts and coconut fibers are resistant to bacteria and fungi.
Coconut biomass is available in the form of coconut husk and coconut shells. Coconut husk and shells are an attractive biomass fuel and are also a good source of charcoal. The major advantage of using coconut biomass as a fuel is that coconut is a permanent crop and available round the year so there is constant whole year supply. Activated carbon manufactured from coconut shell is considered extremely effective for the removal of impurities in wastewater treatment processes.
Coconut shell is an agricultural waste and is available in plentiful quantities throughout tropical countries worldwide. In many countries, coconut shell is subjected to open burning which contributes significantly to CO2 and methane emissions.
Coconut shell is widely used for making charcoal. The traditional pit method of production has a charcoal yield of 25–30% of the dry weight of shells used. The charcoal produced by this method is of variable quality, and often contaminated with extraneous matter and soil. The smoke evolved from pit method is not only a nuisance but also a health hazard.
The coconut shell has a high calorific value of 20.8MJ/kg and can be used to produce steam, energy-rich gases, bio-oil, biochar etc. It is to be noted that coconut shell and coconut husk are solid fuels and have the peculiarities and problems inherent in this kind of fuel.
Coconut shell is more suitable for pyrolysis process as it contain lower ash content, high volatile matter content and available at a cheap cost. The higher fixed carbon content leads to the production to a high-quality solid residue which can be used as activated carbon in wastewater treatment. Coconut shell can be easily collected in places where coconut meat is traditionally used in food processing.
Coconut husk has high amount of lignin and cellulose, and that is why it has a high calorific value of 18.62MJ/kg. The chemical composition of coconut husks consists of cellulose, lignin, pyroligneous acid, gas, charcoal, tar, tannin, and potassium.
The predominant use of coconut husks is in direct combustion in order to make charcoal, otherwise husks are simply thrown away. Coconut husk can be transformed into a value-added fuel source which can replace wood and other traditional fuel sources. In terms of the availability and costs of coconut husks, they have good potential for use in power plants.
Biomass logistics include all the unit operations necessary to move biomass feedstock from the land to the biomass energy plant and to ensure that the delivered feedstock meets the specifications of the conversion process. The packaged biomass can be transported directly from farm or from stacks next to the farm to the processing plant.
Biomass may be minimally processed (i.e. ground) before being shipped to the plant, as in case of biomass supply from the stacks. Generally the biomass is trucked directly from farm to biomass energy plant if no processing is involved.
Another option is to transfer the biomass to a central location where the material is accumulated and subsequently dispatched to the energy conversion facility. While in depot, the biomass could be pre-processed minimally (ground) or extensively (pelletized). The depot also provides an opportunity to interface with rail transport if that is an available option.
The choice of any of the options depends on the economics and cultural practices. For example in irrigated areas, there is always space on the farm (corner of the land) where quantities of biomass can be stacked. The key components to reduce costs in harvesting, collecting and transportation of biomass can be summarized as:
Reduce the number of passes through the field by amalgamating collection operations.
Increase the bulk density of biomass
Work with minimal moisture content.
Granulation/pelletization is the best option, though the existing technology is expensive.
Trucking seems to be the most common mode of biomass transportation option but rail and pipeline may become attractive once the capital costs for these transport modes are reduced.
The logistics of transporting, handling and storing the bulky and variable biomass material for delivery to the bioenergy processing plant is a key part of the biomass supply chain that is often overlooked by project developers. Whether the biomass comes from forest residues on hill country, straw residues from cereal crops grown on arable land, or the non-edible components of small scale, subsistence farming systems, the relative cost of collection will be considerable.
Careful development of a system to minimize machinery use, human effort and energy inputs can have a considerable impact on the cost of the biomass as delivered to the processing plant gate.
The logistics of supplying a biomass power plant with sufficient volumes of biomass from a number of sources at suitable quality specifications and possibly all year round, are complex. Agricultural residues can be stored on the farm until needed. Then they can be collected and delivered directly to the conversion plant on demand. Infact, this requires considerable logistics to ensure only a few days of supply are available on-site but that the risk of non-supply at any time is low.
The cultivation of rice results in two major types of biomass wastes – Straw and Husk –having attractive potential in terms of biomass energy. Although the technology for rice husk utilization is well-proven in industrialized countries of Europe and North America, such technologies are yet to be introduced in the developing world on commercial scale.
The importance of Rice Husk and Rice Straw as an attractive source of energy can be gauged from the following statistics:
1 ton of Rice paddy produces 290 kg Rice Straw
290 kg Rice Straw can produce 100 kWh of power
Calorific value = 2400 kcal/kg
1 ton of Rice paddy produces 220 kg Rice Husk
1 ton Rice Husk is equivalent to 410- 570 kWh electricity
Calorific value = 3000 kcal/kg
Moisture content = 5 – 12%
Rice husk is the most prolific agricultural residue in rice producing countries around the world. It is one of the major by-products from the rice milling process and constitutes about 20% of paddy by weight. Rice husk, which consists mainly of lingo-cellulose and silica, is not utilized to any significant extent and has great potential as an energy source.
Rice husk can be used for power generation through either the steam or gasification route. For small scale power generation, the gasification route has attracted more attention as a small steam power plant is very inefficient and is very difficult to maintain due to the presence of a boiler. In addition for rice mills with diesel engines, the gas produced from rice husk can be used in the existing engine in a dual fuel operation.
The benefits of using rice husk conversion technology are numerous. Primarily, it provides electricity and serves as a way to dispose of agricultural waste. In addition, steam, a byproduct of power generation, can be used for paddy drying applications, thereby increasing local incomes and reducing the need to import fossil fuels. Rice husk ash, the byproduct of rice husk power plants, can be used in the cement and steel industries further decreasing the need to import these materials.
Rice straw can either be used alone or mixed with other biomass materials in direct combustion. In this technology, combustion boilers are used in combination with steam turbines to produce electricity and heat. The energy content of rice straw is around 14 MJ per kg at 10 percent moisture content. The by-products are fly ash and bottom ash, which have an economic value and could be used in cement and/or brick manufacturing, construction of roads and embankments, etc.
Straw fuels have proved to be extremely difficult to burn in most combustion furnaces, especially those designed for power generation. The primary issue concerning the use of rice straw and other herbaceous biomass for power generation is fouling, slagging, and corrosion of the boiler due to alkaline and chlorine components in the ash. Europe, and in particular, Denmark, currently has the greatest experience with straw fired power and CHP plants.
South Africa is experiencing a mammoth energy crisis with its debt-laden national power utility, Eskom, being unable to meet the electricity needs of the nation. After extensive periods of load shedding in 2018 and again earlier this year, it is becoming increasingly important to find an alternative source of energy. According to Marko Nokkala, senior sales manager at VTT Technical Research Centre of Finland, South Africa is in the perfect position to utilize biomass as an alternative source of energy.
Things to Consider
Should South Africa choose to delve deeper into biomass energy production, there are a few things that need to be considered. At present, a lot of biomass (such as fruit and vegetables) is utilized as food. It will, therefore, be necessary to identify alternative biomass sources that are not typically used as food, so that a food shortage is never created in the process.
One alternative would be to use municipal solid waste from landfills and dumpsites as well as the wood waste from the very large and lucrative forestry industry in the country. It is also essential to keep in mind that an enormous amount of biomass will be needed to replace even a portion of the 90 million tons of coal that Eskom utilizes every year at its various power stations.
Potential Biomass Conversion Routes
There are a number of processing technologies that South Africans can utilize to turn their biomass into a sustainable energy source. Biochemical conversion involving technology such as anaerobic digestion and fermentation makes use of enzymes, microorganisms, and bacteria to breakdown the biomass into a variety of liquid or vaporous fuels.
Fermentation is especially suitable when the biomass waste boasts a high sugar or water content, as is the case with a variety of agricultural wastes. By placing some focus on microbial fermentation process development, a system can effectively be created that will allow for large-scale biofuel production. Other technologies to consider include thermal methods like co-firing, pyrolysis, and gasification.
Future of biomass energy in South Africa
Despite the various obstacles that may slow down the introduction of large-scale biomass energy production in the country, it still promises to be a viable solution to the pressing energy concern. Biomass energy production does not require any of the major infrastructures that Eskom is currently relying on.
Although the initial setup will require a substantial amount of electricity, running a biomass conversion plant will cost significantly less than a coal-powered power plant in the long run. With the unemployment rate hovering around 27.1% in South Africa at present, any jobs created through the implementation of biomass energy conversion will be of great benefit to the nation.
Without speedy intervention, South Africa may very soon be left in the dark. Although there are already a number of wind farms in operation in the country, the addition of biomass conversion facilities will undoubtedly be of great benefit to Africa’s southernmost country.
Vietnam is one of the few countries having a low level of energy consumption in the developing world with an estimated amount of 210 kg of oil equivalent per capita/year. A significant portion of the Vietnamese population does not have access to electricity. Vietnam is facing the difficult challenge of maintaining this growth in a sustainable manner, with no or minimal adverse impacts on society and the environment.
Being an agricultural country, Vietnam has very good biomass energy potential. Agricultural wastes are most abundant in the Mekong Delta region with approximately 50% of the amount of the whole country and Red River Delta with 15%. Major biomass resources includes rice husk from paddy milling stations, bagasse from sugar factories, coffee husk from coffee processing plants in the Central Highlands and wood chip from wood processing industries. Vietnam has set a target of having a combined capacity of 500 MW of biomass power by 2020, which is raised to 2,000 MW in 2030.
Rice husk and bagasse are the biomass resources with the greatest economic potential, estimated at 50 MW and 150 MW respectively. Biomass fuels sources that can also be developed include forest wood, rubber wood, logging residues, saw mill residues, sugar cane residues, bagasse, coffee husk and coconut residues.
Currently biomass is generally treated as a non-commercial energy source, and collected and used locally. Nearly 40 bagasse-based biomass power plants have been developed with a total designed capacity of 150 MW but they are still unable to connect with the national grid due to current low power prices. Five cogeneration systems selling extra electricity to national grid at average price of 4 US cents/kWh.
Biogas potential is approximately 10 billion m3/year, which can be collected from landfills, animal excrements, agricultural residues, industrial wastewater etc. The biogas potential in the country is large due to livestock population of more than 30 million, mostly pigs, cattle, and water buffalo. Although most livestock dung already is used in feeding fish and fertilizing fields and gardens, there is potential for higher-value utilization through biogas production.
It is estimated that more than 25,000 household biogas digesters with 1 to 50 m3, have been installed in rural areas. The Dutch-funded Biogas Program operated by SNV Vietnam constructed some 18,000 biogas facilities in 12 provinces between 2003 and 2005, with a second phase (2007-2010) target of 150,000 biogas tanks in both rural and semi-urban settings.
Municipal solid waste is also a good biomass resource as the amount of solid waste generated in Vietnam has been increasing steadily over the last few decades. In 1996, the average amount of waste produced per year was 5.9 million tons per annum which rose to 28 million tons per in 2008 and expected to reach 44 million tons per year by 2015.
Date palm trees produce huge amount of agricultural wastes in the form of dry leaves, stems, pits, seeds etc. A typical date tree can generate as much as 20 kilograms of dry leaves per annum while date pits account for almost 10 percent of date fruits.
Date palm biomass is found in large quantities across the Middle East
Date palm is considered a renewable natural resource because it can be replaced in a relatively short period of time. It takes 4 to 8 years for date palms to bear fruit after planting, and 7 to 10 years to produce viable yields for commercial harvest. Usually date palm wastes are burned in farms or disposed in landfills which cause environmental pollution in dates-producing nations.
The major constituents of date palm biomass are cellulose, hemicelluloses and lignin. In addition, date palm has high volatile solids content and low moisture content. These factors make date palm residues an excellent biomass resource in date-palm producing nations.
Date palm biomass is an excellent resource for charcoal production in Middle East
A wide range of physico-chemical, thermal and biochemical technologies exists for sustainable utilization of date palm biomass. Apart from charcoal production and energy conversion (using technologies like combustion and gasification), below are few ways for utilization of date palm wastes:
Conversion into fuel pellets or briquettes
Biomass pellets are a popular type of alternative fuel (analogous to coal), generally made from wood wastes and agricultural biomass. The biomass pelletization process consists of multiple steps including pre-treatment, pelletization and post-treatment of biomass wastes. Biomass pellets can be used as a coal replacement in power plant, industries and other application.
Conversion into energy-rich products
Biomass pyrolysis is the thermal decomposition of date palm biomass occurring in the absence of oxygen. The products of biomass pyrolysis include biochar, bio-oil and gases including methane, hydrogen, carbon monoxide, and carbon dioxide.
Depending on the thermal environment and the final temperature, pyrolysis will yield mainly biochar at low temperatures, less than 450 0C, when the heating rate is quite slow, and mainly gases at high temperatures, greater than 800 0C, with rapid heating rates. At an intermediate temperature and under relatively high heating rates, the main product is bio-oil.
Bio-oil can be upgraded to either a special engine fuel or through gasification processes to a syngas which can then be processed into biofuels. Bio-oil is particularly attractive for co-firing because it can be more readily handled and burned than solid fuel and is cheaper to transport and store.
Conversion into biofertilizer
Composting is the most popular method for biological decomposition of organic wastes. Date palm waste has around 80% organic content which makes it very well-suited for the composting process. Commercial-scale composting of date palm wastes can be carried out by using the traditional windrow method or a more advanced method like vermicomposting.
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