Collection Systems for Agricultural Biomass

Biomass collection involves operations pertaining to gathering, packaging, and transporting biomass to a nearby site for temporary storage. The amount of biomass resource that can be collected at a given time depends on a variety of factors. In case of agricultural residues, these considerations include the type and sequence of collection operations, the efficiency of collection equipment, tillage and crop management practices, and environmental restrictions, such as the need to control soil erosion, maintain soil productivity, and maintain soil carbon levels.

The most conventional method for collecting biomass is baling which can be either round or square. Some of the important modern biomass collection operations have been discussed below:

Baling

Large square bales are made with tractor pulled balers. A bale accumulator is pulled behind the baler that collects the bales in group of 4 and leaves them on the field. At a later date when available, an automatic bale collector travels through the field and collects the bales.

The automatic bale collector travels to the side of the road and unloads the bales into a stack. If the automatic bale collector is not available bales may be collected using a flat bed truck and a front end bale loader. A loader is needed at the stack yard to unload the truck and stack the bales. The stack is trapped using a forklift and manual labor.

Loafing

When biomass is dry, a loafer picks the biomass from windrow and makes large stacks. The roof of the stacker acts as a press pushing the material down to increase the density of the biomass. Once filled, loafer transports the biomass to storage area and unloads the stack. The top of the stack gets the dome shape of the stacker roof and thus easily sheds water.

Dry Chop

In this system a forage harvester picks up the dry biomass from windrow, chops it into smaller pieces (2.5 – 5.0 cm). The chopped biomass is blown into a forage wagon traveling along side of the forage harvester. Once filled, the forage wagon is pulled to the side of the farm and unloaded. A piler (inclined belt conveyor) is used to pile up the material in the form of a large cone.

Wet Chop

Here a forage harvester picks up the dry or wet biomass from the windrow. The chopped biomass is blown into a forage wagon that travels along side of the harvester. Once filled, the wagon is pulled to a silage pit where biomass is compacted to produce silage.

Whole Crop Harvest

The entire material (grain and biomass) is transferred to a central location where the crop is fractionated into grain and biomass.  The McLeod Harvester developed in Canada fractionates the harvested crop into straw and graff (graff is a mixture of grain and chaff). The straw is left on the field. Grain separation from chaff and other impurities take place in a stationary system at the farmyard.

McLeod Harvester fractionates the harvested crop into straw and graff

For the whole crop baling, the crop is cut and placed in a windrow for field drying. The entire crop is then baled and transported to the processing yard. The bales are unwrapped and fed through a stationary processor that performs all the functions of a normal combine. Subsequently, the straw is re-baled.

Biomass Energy Potential in Philippines

The Philippines has abundant supplies of biomass energy resources in the form of agricultural crop residues, forest residues, animal wastes, agro-industrial wastes, municipal solid wastes and aquatic biomass. The most common agricultural wastes are rice hull, bagasse, cane trash, coconut shell/husk and coconut coir. The use of crop residues as biofuels is increasing in the Philippines as fossil fuel prices continue to rise. Rice hull is perhaps the most important, underdeveloped biomass resource that could be fully utilized in a sustainable manner.

At present, biomass technologies utilized in the country vary from the use of bagasse as boiler fuel for cogeneration, rice/coconut husks dryers for crop drying, biomass gasifiers for mechanical and electrical applications, fuelwood and agricultural wastes for oven, kiln, furnace and cook-stoves for cooking and heating purposes. Biomass technologies represent the largest installations in the Philippines in comparison with the other renewable energy, energy efficiency and greenhouse gas abatement technologies.

Biomass energy plays a vital role in the nation’s energy supply. Nearly 30 percent of the energy for the 80 million people living in the Philippines comes from biomass, mainly used for household cooking by the rural poor. Biomass energy application accounts for around 15 percent of the primary energy use in the Philippines. The resources available in the Philippines can generate biomass projects with a potential capacity of more than 200 MW.

Almost 73 percent of this biomass use is traced to the cooking needs of the residential sector while industrial and commercial applications accounts for the rest. 92 percent of the biomass industrial use is traced to boiler fuel applications for power and steam generation followed by commercial applications like drying, ceramic processing and metal production. Commercial baking and cooking applications account for 1.3 percent of its use.

The EC-ASEAN COGEN Programme estimated that the volume of residues from rice, coconut, palm oil, sugar and wood industries is 16 million tons per year. Bagasse, coconut husks and shell can account for at least 12 percent of total national energy supply. The World Bank-Energy Sector Management Assistance Program estimated that residues from sugar, rice and coconut could produce 90 MW, 40 MW, and 20 MW, respectively.

The development of crop trash recovery systems, improvement of agro-forestry systems, introduction of latest energy conversion technologies and development of biomass supply chain can play a major role in biomass energy development in the Philippines. The Philippines is among the most vulnerable nations to climatic instability and experiences some of the largest crop losses due to unexpected climatic events. The country has strong self-interest in the advancement of clean energy technologies, and has the potential to become a role model for other developing nations on account of its broad portfolio of biomass energy resources and its potential to assist in rural development.

Agricultural Wastes in the Philippines

The Philippines is mainly an agricultural country with a land area of 30 million hectares, 47 percent of which is agricultural. The total area devoted to agricultural crops is 13 million hectares distributed among food grains, food crops and non-food crops. Among the crops grown, rice, coconut and sugarcane are major contributors to biomass energy resources.

The most common agricultural wastes in the Philippines are rice husk, rice straw, coconut husk, coconut shell and bagasse. The country has good potential for biomass power plants as one-third of the country’s agricultural land produces rice, and consequently large volumes of rice straw and hulls are generated.

Rice is the staple food in the Philippines. The Filipinos are among the world’s biggest rice consumers. The average Filipino consumes about 100 kilograms per year of rice.  Though rice is produced throughout the country, the Central Luzon and Cagayan Valley are the major rice growing regions. With more than 1.2 million hectares of rain-fed rice-producing areas, the country produced around 16 million tons of rice in 2007. The estimated production of rice hull in the Philippines is more than 2 million tons per annum which is equivalent to approximately 5 million BOE (barrels of oil equivalent) in terms of energy. Rice straw is another important biomass resource with potential availability exceeding 5 million tons per year across the country.

With the passing of Biofuels Act of 2006, the sugar industry in the Philippines which is the major source of ethanol and domestic sugar will become a major thriving industry. Around 380,000 hectares of land is devoted to sugarcane cultivation. It is estimated that 1.17 million tonnes of sugarcane trash is recoverable as a biomass resource in the Philippines. In addition, 6.4 million tonnes of surplus bagasse is available from sugar mills. There are 29 operating sugar mills in the country with an average capacity of 6,900 tonnes of cane per day. Majority is located in Negros Island which provides about 46% of the country’s annual sugar production.

The Philippines has the largest number of coconut trees in the world as it produces most of the world market for coconut oil and copra meal. The major coconut wastes include coconut shell, coconut husks and coconut coir dust. Coconut shell is the most widely utilized but the reported utilization rate is very low.  Approximately 500 million coconut trees in the Philippines produce tremendous amounts of biomass as husk (4.1 million tonnes), shell (1.8 million tonnes), and frond (4.5 million tonnes annually).

Maize is a major crop in the Philippines that generates large amounts of agricultural residues. It is estimated that 4 million tonnes of grain maize and 0.96 million tonnes of maize cobs produced yearly in the Philippines. Maize cob burning is the main energy application of the crop, and is widely practiced by small farmers to supplement fuelwood for cooking.

A Primer on Agricultural Residues

The term agricultural residue is used to describe all the organic materials which are produced as by-products from harvesting and processing of agricultural crops. These residues can be further categorized into primary residues and secondary residues. Agricultural residues, which are generated in the field at the time of harvest, are defined as primary or field based residues whereas those co-produced during processing are called secondary or processing based residues.

  • Primary residues – paddy straw, sugarcane top, maize stalks, coconut empty bunches and frond, palm oil frond and bunches;
  • Secondary residues – paddy husk, bagasse, maize cob, coconut shell, coconut husk, coir dust, saw dust, palm oil shell, fiber and empty bunches, wastewater, black liquor.

Agricultural residues are highly important sources of biomass fuels for both the domestic and industrial sectors. Availability of primary residues for energy application is usually low since collection is difficult and they have other uses as fertilizer, animal feed etc. However secondary residues are usually available in relatively large quantities at the processing site and may be used as captive energy source for the same processing plant involving minimal transportation and handling cost.

Crop residues encompasses all agricultural wastes such as straw, stem, stalk, leaves, husk, shell, peel, pulp, stubble, etc. which come from cereals (rice, wheat, maize or corn, sorghum, barley, millet), cotton, groundnut, jute, legumes (tomato, bean, soy) coffee, cacao, tea, fruits (banana, mango, coco, cashew) and palm oil.

Rice produces both straw and rice husks at the processing plant which can be conveniently and easily converted into energy. Significant quantities of biomass remain in the fields in the form of cob when maize is harvested which can be converted into energy. Sugar cane harvesting leads to harvest residues in the fields while processing produces fibrous bagasse, both of which are good sources of energy. Harvesting and processing of coconuts produces quantities of shell and fibre that can be utilised while peanuts leave shells. All these materials can be converted into useful energy by a wide range of technologies..

Agricultural Biomass in Malaysia

Malaysia is located in a region where biomass productivity is high which means that the country can capitalize on this renewable energy resource to supplements limited petroleum and coal reserves. Malaysia, as a major player in the palm oil and sago starch industries, produces a substantial amount of agricultural biomass waste which present a great opportunity for harnessing biomass energy in an eco-friendly and commercially-viable manner.

Peninsular Malaysia generates large amounts of wood and’ agricultural residues, the bulk of which are not being currently utilised for any further downstream operations. The major agricultural crops grown in Malaysia are rubber (39.67%), oil palm (34.56%), cocoa (6.75%), rice (12.68%) and coconut (6.34%). Out of the total quantity of residues generated, only 27.0% is used either as fuel for the kiln drying of timber, for the manufacture of bricks, the curing of tobacco leaves, the drying rubber-sheets and for the manufacture of products such as particleboard and fibreboard. The rest has to be disposed of by burning.

Palm Oil Industry

Oil palm is one of the world’s most important fruit crops. Malaysia is one of the largest producers and exporter of palm oil in the world, accounting for 30% of the world’s traded edible oils and fats supply. Palm oil industries in Malaysia have good potential for high pressure modern power plants and the annual power generation potential is about 8,000 GWh. Malaysia produced more than 20 million tonnes of palm oil in 2012 over 5 million hectares of land.

The palm oil industry is a significant branch in Malaysian agriculture. Almost 70% of the volume from the processing of fresh fruit bunch is removed as waste in the form of empty fruit bunches (EFBs), fibers and shells, as well as liquid effluent. Fibres and shells are traditionally used as fuels to generate power and steam. Effluents are sometimes converted into biogas that can be used in gas-fired gensets.

Sugar Industry

The cultivation of sugarcane in Malaysia is surprisingly small. Production is concentrated in the Northwest extremity of peninsular Malaysia in the states of Perlis and Kedah. This area has a distinct dry season needed for cost-efficient sugarcane production. Plantings in the states of Perak and Negri Sembilan were unsuccessful due to high unit costs as producing conditions were less suitable.

The lack of growth in cane areas largely reflects the higher remuneration received by farmers for other crops, especially oil palm. Over the past 20 years while the sugarcane area has remained at around 20 000 hectares, that planted to oil palm has expanded from 600 000 hectares to 5 million hectares.

Other leading crops in terms of planted areas are rubber with 2.8 million hectares, rice with 670 000 hectares and cocoa with 380 000 hectares. Malaysia, the world’s third largest rubber producer, accounted for 1 million tons of natural rubber production in 2012. Like oil palm industry, the rubber industry produces a variety of biomass wastes whose energy potential is largely untapped until now.