Clean energy, natural solutions. Understanding coconut as a biomass fuel

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1 Understanding coconut as a biomass fuel V1

2 Origins and uses of coconut The coconut palm is a reliable crop that yields not only a highly versatile fruit, but also wood and other valuable materials. The uses for the coconut palm are not only many and varied; but it is relatively easy to grow, harvest and store the crop. The benefits of coconut farming were recognised and adopted by early agrarian cultures, and coconut farming on a vast scale continues to this day. Aside from the obvious culinary uses of coconut oil, meat and liquids, the coconut has been used for a number of historically significant applications: the coir, or fibre, to make ropes, brushes and sacks; the thicker fronds for brooms, baskets and even arrows. Husks and shells have traditionally been used for utensils and even applied in medicinal contexts. It is therefore intriguing that until very recently, the intrinsic value of leftover waste as a fuel or energy source has not been fully developed or exploited. Modern coconut industry Before addressing the pros and cons of coconut waste as a fuel source, it is first important to take a look at the waste materials created by the modern day coconut industry, as these can all be considered as potential biomass feedstock. Today, the Asia-Pacific region is responsible for around 90% of global coconut production. The highest producing nations of coconut in the region are (in order of volume): Indonesia, Philippines, India, Sri Lanka, Thailand and Malaysia. Together, these nations account for roughly 51 million tons of annual output. The outlook for the industry is favourable due to the recent popularity of coconut oil, water and food products. With so many uses, the quantity and nature of coconut waste left after production will also vary depending on the processing methods and the final products, and from market to market. The three most common end products for coconuts are culinary coconut milk or water, coconut oil and desiccated coconut. The harvesting and production processes for these products each leaves behind significant amounts of residue. One of the main advantages of coconut waste as a fuel source is its flexibility and scope of use. The potential from coconut waste is not limited to the shells, but also include husks, fronds, leaves, stems and fibres. All of these resources can be found in abundance in most processing facilities and with the right technology can be used as feedstock to create renewable biomass energy. Coconut as a biomass fuel As a non-seasonal crop, coconut provides a continuous supply of nuts month after month throughout the entire year. Coconut trees also require little to no maintenance once planted and have a very long life (up to 100 fruit bearing years). Thus coconut trees offer a constant and long-lasting supply of economically valuable materials including renewable energy fuel. These advantages are complimented by the vast quantity of coconut waste produced throughout SE Asia and Asia Pacific an estimated annual figure of around 25 million tons. Nevertheless, although coconut

3 waste as biomass feedstock offers numerous advantages, there are also several factors which have hindered its widespread adoption and use. Coconut wastes have a high potential for energy production (see tables below for details). However, despite some niche applications for the use of residues the amount of waste used remains very low, and traditionally coconut farmers dispose of the left over produce by either burning it or leaving it to rot in the fields. In SE Asia, some people use inefficient and polluting small scale processes to make a crude charcoal but the vast majority of waste materials still go unused. Coconut shells and husks various stages of maturity Fuel summary Typical coconut waste (as a percentage of total mass) includes shell (12%), husks (35-40%) and coir dust (3-4%). Trees also shed about 40 fronds weighing about 10kg each over a 5-6 year period. Thus the regular waste amount averages around 50% of coconut production mass. Coconut husk, one of the most abundant and underutilized residues, is the 5-10 cm thick fibre layer covering the coconut s fruit. Depending on the ripeness of the coconut, the husk appears in colours from light green (when very young) to yellow to brown (when mature). The husks comprise of many stringy fibres surrounded by coir dust. The husks and dust make up about 40% of the fruit s mass. DP CleanTech has developed a method to maximize utilization of coconut wastes by designing a feeding and combustion system capable of handling a mixture of wastes. The below fuel analysis is calculated on a 'standard' mix of coconut residues and fronds based on a solution provided by DP: Fuel mixture of design fuel (%m) Fuel Moisture Content Ratio Coconut residues (shell, husk, bunch) Coconut frond 50% 35% 65% 35% Fuel range (%m) Fuel Coconut residues (shell, husk, bunch) Coconut frond Moisture content of fuel mix Ratio 50-80% 0-50% 30-50%

4 Coconut husks and fibres (unravelled) The coconut residues and fronds will normally be delivered with relatively high moisture content levels. Moisture content and energy values can be seen below: Fuel Coconut residues, as delivered (shell, husk, bunch) Coconut residues, dried (shell, husk, bunch) Coconut frond, as delivered Coconut frond, dried Mixed fuel, as delivered (35% frond, 65% residue) Mixed fuel, dried (35% frond, 65% residue) Moisture content (%m) 50% % % - Lower heat value (MJ/kg) There are a number of reasons that coconut wastes have not been broadly used as renewable energy fuel. Challenges which have traditionally been difficult to overcome include: Moisture content Acid corrosion and fouling Inconsistent shapes, sizes and densities of feedstock In order to reach an economically efficient scale and to maintain power plant availability, these challenges have to be considered. Below we will discuss DP s approach to address and overcome the challenges which are innate to this biomass fuel.

5 Challenging features of coconut waste There are a number of common challenges associated with the use of coconut wastes as a biomass fuel: corrosion, moisture content, fouling, shape and size conformity. These properties are also precisely why DP CleanTech s technology is well suited for utilizing this fuel type to generate renewable energy. Each type of coconut residue (husk, shell, bunch, fronds, leaves and trunk) has different physical properties; and will have varying levels of lignin, cellulose, pectin and moisture. Furthermore, shapes, sizes and densities are not uniform, thereby complicating the design of an efficient fuel handling and combustion process. The collection and transportation of residues from the harvesting or processing locations to a biomass plant may also be challenging and represent an additional cost. How can such challenges be overcome? Proper feasibility studies and planning Fortunately, such challenges can be addressed with proper planning, the right level of expertise and the right technology solutions. Issues such as location of plants near harvesting and production points; grid infrastructure and government policy are important factors in feasibility analysis and project economics. Selecting the right technology for cost effective fuel handling and optimal combustion is also crucial for long term equipment reliability and availability of output. Properly conducted feasibility studies based on end to end evaluation of biomass logistics, economics and technology options are a key area of DP expertise. Fuel expertise analysis, handling and combustion DP has unparalleled expertise in handling difficult or complex fuels, and we have already successfully demonstrated our ability to handle other fuels with similar properties: Moisture content: similar solutions needed for low quality wood wastes and straws Corrosion and fouling: similar solutions needed for straws and MSW Size and shapes: similar solutions needed for MSW Fuel handling: from storage to fuel feeding, DP understands the properties of coconut fuels and can advise on best practices Reliable, proven and advanced technology DP s unique HPHT solutions coupled with our patented water-cooled vibrating grate is the optimal technology for handling all types of coconut waste; and can be designed specifically to overcome the challenges they pose. DP employs this expertise in projects throughout Europe and Asia, and has recently completed a 9.9 MWe Mahachai coconut waste-fired project in Samhut Sakhon project in Thailand using this approach and patented technology.

6 DP s proven solution Based on our knowledge of coconut residues as a design fuel, DP is able to develop solutions to provide efficient energy conversion from this biomass resource. Below are values derived from a Thailand based case study: Fuel: coconut residues (husk, shell, bunch, frond, leaves, trunk) Fuel consumption: 323t/d (45% moisture) or 167t/d (dry) Calorific value: 8.35 MJ/KG Power output: 9.9MWe (gross) Steam flow: 40t/h Steam pressure: 92 bar Steam temperature: 537 C Boiler efficiency: 90% Gross plant efficiency: 31% Availability: >7,900 hours/year DP technology is ideally suited for utilizing all types of coconut residues. It has been adapted and optimised for a wide variety of fuels differing in physical characteristics and chemical properties, overall quality and energy values. Tackling the challenges posed by coconut specifically requires understanding of the fuel as well as state of the art technology. Solution for Mahachai Project, Samut Sakhon Province, Thailand 1 Shredded fuel 7 Belt conveyor 13 Secondary air 19 Boiler feed water 25 Water-cooled condenser 2 Walking floor 8 Pusher feeder 14 Combustion chamber 20 Economizer 26 ESP filter 3 Screw conveyor 9 Hydraulic station 15 Steam drum 21 Flue gas cooler 27 Ash handling 4 Weight cell 10 Vibrating grate 16 Superheater 1 22 Air preheater 1 28 ID fan 5 Non-shredded fuel 11 Slag conveyor 17 Superheater 2 23 Air preheater 2 29 FD fan 6 Feeding hopper 12 Primary air 18 Superheater 3 24 Steam turbine generator 30 Stack Image cannot be reproduced without permission of DP CleanTech v1.1