Wind Data

SARAWAK METEOROLOGICAL MAST DATA

Recorded meteorological mast data was received from Jabatan Meteorologi Malaysia for four sites across Sarawak Sibu, Miri, Kuching and Bintulu airports. The location of these sites can be seen in the following Figure. The wind data provided was an hourly time series of mean wind speeds and direction covering the 2008 calendar year from 01/01/2008 to 31/12/2008 inclusive. The data received at Kuching Airport was at a height of 12.2 m AGL, the other three sites ‘anemometer heights were unknown although in HTC’s experience airport anemometers are generally between 10 m and 15 m AGL.

Figure: Sarawak map of prospective sites and mast data locations

LIMITATIONS OF AIRPORT MAST DATA

Significant limitations are inherent in the mast data provided due to their placement at airports and low height of the anemometers above ground level. Significant uncertainties can occur as a result of turbulence created from wind flow around surrounding buildings and air traffic. The roughness of the ground can impact on the wind speeds by causing non-laminar flow. Due to the nature of airports it is often the case that obstacles are changing over time such as the addition of new buildings or changing surfaces. This can affect the wind speeds when measured at such a low level. Due to these limitations the data is only used to identify trends in the wind speeds such as the changing of magnitude of the wind with time to display diurnal (daily) and seasonal (monthly) variations.

WIND MODELLING

In the absence of extensive site data, HTC has utilised the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) software package known as The Air Pollution Model (TAPM) Version 3 which predicts three-dimensional meteorology and air pollution concentration. TAPM takes high-level synoptic data and produces low-level grids (or time-series) of wind regimes across a defined region for a defined time period.

Studies have been undertaken that verify results against actual mast data to a reasonable degree, thus providing the confidence to apply the TAPM model to a high-level initial-investigation study such as this.

The synoptic data used in this study was sourced from the CSIRO for the year 2008. Output from the model can be extracted as low as 10 m and is also available at 25 m, 50 m 75 m, 100 m, 150 m and then numerous levels up to 3000 m above ground level.

For this study the hub heights of likely turbines are around 75 m above ground level. However, the modelled data is based on coarse resolution terrain and surface roughness classes so it is not recommended that data at this close to the surface be used. Verification studies by HTC have consistently shown that the wind speed predicted by TAPM best matches wind speeds measured by a mast at lower heights (i.e. wind speed at 75 m in TAPM does not equate to wind speed measured by a mast at 75 m). 

Consequently, the approach taken was to extract data from the TAPM model at a height of 150 m to best represent the expected wind speed at an approximate 75 m hub height based on HTC experience.

VALIDATION OF TAPM

Validation of the TAPM model was performed by comparing generated wind data sets with the supplied mast data. TAPM was used to create an hourly time series for the year of 2008 at a height of 10 m AGL at each of the four airport sites Sibu, Miri, Kuching and Bintulu, where mast data was received. This generated time series was then compared against actual mast data to observe relationships between the two datasets and identify any significant features.

The modelled TAPM wind speeds were extracted at 10 m and 150 m AGL for each mast location and plotted against the site data. Correlations between the data sets, as well as seasonal and diurnal (daily) trends were assessed.

For further details log on website :
http://www.sarawakenergy.com.my/index.php/r-d/wind-energy/wind-data

Wind Energy

INTRODUCTION TO WIND ENERGY

Sarawak Energy Berhad (SEB) is studying the renewable energy potential in Sarawak. One element of this process is the identification of suitable sites for wind energy capture. SEB is seeking to identify sites in Sarawak where wind energy capture would be economically, socially and environmentally viable. This report provides a wind resource map of suitable resolution to underpin SEB site selection activities.

The coarse resolution wind resource map presents a modelled mean wind speed for the year 2008 at 75 m Above Ground Level (AGL) a nominal wind turbine hub height. The purpose of the Sarawak wind resource map is to identify areas of higher relative mean wind speeds across the state. The year 2008 may not necessarily be representative of the long-term average wind speed. However, the 2008 year was used as it matches the airport mast data provided for 2008 and allowed correlations between the two data sets. 

In general, the modelled data is best applied to compare the wind speed between different regions to identify locations with better potential for wind energy (and then focusing efforts on those regions), or as a long-term data source in the absence of other data to look at long-term trends. Consequently the results of modelled data should be considered to be an indication of relative wind speeds rather than absolute wind speeds, and on-site monitoring is required to determine actual wind speeds. On site monitoring should then be used to develop a business case.

For further details log on website :
http://www.sarawakenergy.com.my/index.php/r-d/wind-energy

Micro Hydro

SURVEY OF MICRO-HYDRO POTENTIAL IN SARAWAK

INTRODUCTION

There are great potentials for micro-hydro power in Sarawak, especially for the many scattered communities who have no access to the power grid.
The vast networks of rivers and streams found in the rugged terrains amongst the scattered rural population within the vast land area of provide great potentials for this kind of sustainable renewable energy.

MAPPING AREAS

A total of 104 sites/settlements in 8 divisions throughout the state of Sarawak as per Figure below was visited and surveyed in this mapping works, namely;

• Samarahan Division
• Sri Aman Division
• Betong Division
• Sarikei Division
• Kapit Division
• Bintulu Division
• Miri Division
• Limbang Division

Figure: The State of Sarawak

Each of these 8 divisions actually have its sources of water tributaries from the mountain ranges that stretch from the South to the North of Sarawak that flows into the main rivers in the state as follows:

Figure: Sarawak’s terrain

The rural population is scattered either along the river upstream or in the highlands which are far off from the power grid. These areas are accessible either by boats or travelling through logging roads. Almost all settlements are located either near to or along the rivers or streams. The distances of the potential source of hydro power ranges from less than a kilometre to almost 5 kilometres. At present most of these settlements are using small generator sets as source of power for their electricity.

TECHNICAL APPROACH

The technical approach to this survey/mapping was to collect data as well as to record the locations of the settlements, their potential sources and calculate the power producing potential of every source within each of the settlement. No other feasibility assessments were done. The minimum and maximum water levels in all streams/rivers were based on the information or experiences from local dwellers/settlers. This also includes the adverse dry weather conditions during the period of May to October 2009.

Locations of settlements are identified by use of Geographic Information System equipment, the portable handheld Global Positioning System (GPS) unit. It determines the latitude and longitude of the locations. The GPS unit is also used in trekking the routes of each source from the settlements by giving its estimated distances and in determining the estimated hydraulic head of the source.

The calculation of power potential of the streams/rivers requires two values: the flow rate and the hydraulic head corresponding to the elevation difference between the upstream and the downstream ends of the reach. The flow rate was calculated based on the average speed across the stream/river and its average cross sectional area. The power potential values are gross power values based on the estimated flow rates obtained during the day of survey.

 The subsections that follow describe the details of the various aspects of the technical approach in the calculation of the power potential and data analysis in producing the mapping.

THEORY

The calculation of the stream flow rate, hydraulic head and subsequently, power potential is based on the data and information being collected on the ground during the day of survey. That could mean that the water flow at that time could either be between the minimum and maximum range of flow.

Flow Rate Calculations

The flow rate was calculated using the average cross sectional area of the stream and the average velocity across that cross sectional area of stream. The velocity of stream was taken using s stream flow meter. The flow meter consists of an impeller which rotates and a counter will count the number of impeller revolutions per minute.

The flow speed is given by the following formula;

V = 0.000854 C + 0.05

Where
V = velocity in metres/second
C = counts per minute (impeller rotations/minute)
The estimated flow rate is calculated using the equation;
Q = A x V
Where
Q = estimated flow rate in cubic metres/second
A = average cross sectional area of stream in square metre
V = average velocity of stream in metre/second

POWER POTENTIAL CALCULATION

The power potential of a stream was calculated using the hydraulic head and the estimated flow rate. The hydraulic head associated with each stream was obtained using elevation data from the handheld GPS unit. It provides the elevation data at the upstream and the downstream ends of reach. The difference of these elevation values was the hydraulic head for the flow.
 

The following equation was used to calculate the power potential;

P = g x Q x H

Where
P = Power in kilowatts
g = accelaration due to gravity, 9.81 metre/second2
Q = estimated flow rate in cubic metres/second
H = hydraulic head in metre

DATA

All data collected are in both hardcopy and also stored in the GPS memory. These data will be logged into a spatial database management system with the assistance of the GIS section. The data are then transformed into a mapping data which will show the locations of the micro hydro resources and potential.

SITES SURVEYED & DATA ANALYSED

The following are the settlements that have been surveyed for potential micro hydro

For further details log on website :
http://www.sarawakenergy.com.my/index.php/r-d/micro-hydro

Tidal Energy

BACKGROUND

Marine power can be classified into two, namely wave energy and tidal energy. Waves are created by the interaction of wind with the surface of the sea, and they have the potential to provide an unlimited source of renewable energy. Wave energy can be extracted and converted into electricity by wave power machines. These machines can be deployed either on the shoreline or in deeper waters offshore.

Tidal energy exploits the natural ebb and flow of coastal tidal waters caused principally by the interaction of the gravitational fields of the earth, moon and sun. Due to these gravitational forces, water levels follow periodic highs and lows. Associated with these water level changes, there are tidal currents. The tidal energy generator uses this phenomenon to generate energy. The stronger the tide, either in water level height or tidal current velocities, the greater the potential for tidal energy generation.

Tidal power can be extracted with two techniques, namely tidal barrage and tidal stream technology. Tidal barrages make use of the potential energy in the difference in height (or head) between high and low tides, while tidal stream technology makes use of the kinetic energy of moving water to power turbines. Tidal stream method is gaining in popularity because of the lower cost and lower ecological impact compared to barrage.

TIDAL BARRAGE

A dam or barrage is built across an estuary or bay in order to let water flow through it into the basin as the tide comes in. The barrage has gates which allow the water to pass through, thereby filling the basin. The gates are closed when the tide has stopped coming in, indicating the beginning of ebb. The water level outside the basin continues to drop during ebb while the water level inside the basin remains high. The difference of water level creates a ‘head’ or ‘fall’. The water in the basin is then released into the sea through a set of turbines. Power is thereby generated by the turbines. This takes place during ebb and continues until the tide floods and the rising water reduces the head to the minimum operating point. The water is then captured again and the process repeats. The generation of power happens during the ebbs and therefore this mode of operation is called “ebb generation”.

Though there are other modes of operation, like “flood generation” (generating power during floods) and “two-way generation” (generating power during both the floods and ebbs) but these modes of operation are not generally flavoured. “Flood generation” is in general much less efficient than “ebb generation” because the ‘head’ created is usually less than the ‘head’ created by “ebb generation’. While it is possible for “two-way generation” to generate power almost continuously, the extra length needed for the barrage contributes tremendously to the cost of construction.

The cost associate with a tidal barrage will depend on the size of the scheme and its location. Very often the building of a tidal barrage requires a high capital. It is therefore not an attractive proposition to investors due to long payback periods.

Perhaps the biggest drawback of tidal barrage is environmental and ecological. The change in water level and possible flooding would affect the ecosystems along the coast. The water quality in the basin would also be affected, and the turbidity may affect the animals that live in the water. These issues are very delicate, and need to be independently assessed.

For further details log on website :
http://www.sarawakenergy.com.my/index.php/r-d/tidal-energy

Paddy Residues Potential

Sarawak is revising its rice production target to become 100 % self sufficient from 70% self sufficiency level under the Ninth Malaysian Plan (9MP) as a major pace to address food security. Currently, Sarawak is the nation's fourth largest rice producer, after Kedah, Perak and Kelantan. Sarawak had achieved a self-sufficiency level of 53 % with total rice production of 124,544 metric tons (or equivalent to 207,573 metrictons of paddy).

A total of 43,821 hectares in eight areas, including Paloh, Pulau Bruit, Sungai Sebelak, Lingga, Banting, Stumbin, Bijat and Samarahan was identified as suitable for large-scale paddy production in the state. The state government would embark on the development of the Sungai Sebelak area at Roban, involving 3,537 hectares, as the first granary to be implemented under the 9MP. The state government had started the rice estate in Tulai, Bintangor. The preliminary work on Polah has begun with a total of 8,080 ha of paddy field.

Assuming rice yield per hectare is 2.8 ton/hectare, the additional production in future is about 15,650 metric tons per annum. However, the total production shall be higher as the state aims to increase the existing paddy yield of 2.8 metric tons to four metric tons per hectare annually, through the implementation of paddy infrastructure improvement projects, besides promoting the use of high-yield varieties such as MR219, MR220 and MR232 or hybrid paddy for double crop planting.

The total production will be more than 280,000 tons of paddy upon the plans are fully developed in five years. This implies that there are about 70,000 tons of rice husks and 350,000 tons rice straw will be procured from the state paddy industry. If all rice hulls were used in gasification or combustion systems with an overall efficiency of 32 %, the state’s technical energy potential from rice husks alone can be estimated be around of energy corresponding to 592,013 MWh electricity.

PADDY RESIDUES FOR ELECTRICITY

Rice husk can be used for power generation through either the thermal or biological route which can produce biogas of components as such in the following Table. For small scale power generation, the thermal route has attracted more attention as the biological route is still under debate. 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. Attempts have been made in several rice producing countries in Asia to develop rice husk gasification plants for power generation and in some countries rice husk gasification plants have been produced for commercial purpose.

Components	Percentage (%)
Carbon dioxide (CO2)	30.7
Hydrogen sulphide (H2S)	2.1
Carbon monoxide (CO)	9.9
Methane & water vapor	52.3

Table: Percentages of the components of biogas from rice husk

It was envisaged that there are potential for better utilization of rice husks and rice straw for energy production particularly for stationary electricity generation. Practically in short terms, we shall look into the possibilities to produce biogas through anaerobic digestion and gasification which serve as bio-fuel for power generation. This will be profound thought for rural electrification as part of our CSR. With this respect, as in the rural rice growing areas that are not connected to the electricity grid systems, there is a potential of gasifying rice husks and rice straw to provide energy. A gasifier can be coupled to the mill so that the gas products are burnt to supply energy for running the mills. This is an aspect of energy conservation for medium-scale industries in the state.

In a wider perspective, where the volume of rice husk and rice straw is sufficient we shall optimize the use of rice husk and rice straw for larger capacity of gasification system or production of digesters gas and power generation to supply the electricity to the grid. This could be realized when the large scale paddy fields were in operation. Other possible ways of using the residues is to incorporate gasification equipment to a small fuel cell system in the paddy village. This might be of the viable utilization patterns in near future as the technologies of stand-alone court-yard fuel cell systems are getting more reliable. The approach is running the biogas produced into a fuel cell.

PADDY RESIDUES FOR BIOGAS PRODUCTION

New / Extend Paddy Field	Area (ha)
Limbang Valley	20,000
Paloh	8,080
Sg. Seblak	3,537
Daro	2,851
Bijat/Stumbin	2,900
Pulau Bruit	3,353
Lingga/Banting	2,200
Nanga Merit	900
Total	43,821

Table: Proposed new paddy area in Sarawak

Table above shows the total proposed area for paddy field is almost 44,000 ha but at scattered locations. Therefore, SEB has plans for these rural areas the electrification system generated by renewable energy such as hybrid system from wind, solar, mini-hydro to be integrated with fossil generation. There are possibilities to utilize indigenous agriculture biomass like rice husk and rice straw to be gasified or through biochemical process like anaerobic digestion to produce biogas for generating electricity. This may further reduce or displace fossil fuel in providing power to the rural folks. The divisional production of paddy in Sarawak is shown in Table below.

Division	Paddy (ha)
	2005	2006	2007
Kuching	7,008	6,827	6,290
Sri Aman	19,466	19,377	19,314
Sibu	12,037	13,959	12,304
Miri	13,366	12,640	11,337
Limbang	4,680	4,700	4,503
Sarikei	10,785	11,537	11,399
Kapit	19,400	19,234	12,660
Samarahan	14,588	14,145	14,126
Bintulu	7,631	7,093	6,869
Mukah	6,883	6,853	7,730
Betong	11,376	11,152	11,013
Total	127,220	127,517	117,545

Table: Yield and production of paddy by Division 2007

Of  notable area to be looked into for adopting this facility is Nanga Merit in Kapit with current farming area of about 150 ha paddy area under DID irrigation schemes. The village is not connected to SEB’s grid and using diesel generator for electricity. With the expansion of paddy field to 900 ha in near future, the biomass residues from paddy shall be significant to be utilized for generating electricity for the benefit of the villagers. It was estimated 2,520 tons of paddy will be harvested in which about 630 tons of rise husk and 3,150 tons of rice straw can be utilized. This amount of biomass residues could potentially produce 60 TJ of energy which represent 16,650 MWh of electricity. The future potential of power that can be generated from paddy residues is shown in the following Table.

	Area (ha)	Paddy Production (tpa)	RH Generation (tpa)	RS Generation (tpa)	Electricity Potential, 32% efficiency (MW)
Current	150	420	105	525	0.10
Future	900	2,520	630	3,150	0.61

Table: Case study - Nanga Merit

From our initial analysis, there are several districts that show the potential of using paddy residues to produce biogas and then electricity.  There are Sri Aman, Lubok Antu, Simunjan, Daro and Saratok with substantial capacity as shown in Table below. The introduction of large scale paddy fields plantation will further make possible of getting sufficient paddy residues to be feasible to utilize the biomass for power generation.

Properties	Sri Aman	Lubok Antu	Simunjan	Daro	Saratok
Paddy Yield (ton/yr)	23,026	18,324	14,287	11,545	12,750
RH (ton/yr)	5756.5	4581	3571.75	2886.25	3187.5
RS (ton/yr)	28782.5	22905	17858.75	14431.3	15937.5
Power Capacity (MW)	17.37	13.82	10.78	8.71	9.62
Power Output - 32% η (MW)	5.56	4.42	3.45	2.79	3.08

Table: Potential areas (Districts) for generating electricity from paddy residues

 

COGENERATION

Rice husk can be considered as fuel for heat and power generation provided the waste volume is sufficient and regular. Generally, co-generation systems are only feasible for rice mills with a minimum production capacity of 5 tons per hour.
The rice-husk cogeneration system in Pendang, Kedah (steam boiler 6.5 t/h, 30 bar, 450 kWh back pressure turbine and heat exchanger (1,200,000 kcal/hr) is being used for 3 months for heating (paddy drying) as well as supplying power for the plants. Typical size of boiler for rice mills is 5-15 tons/hours coupled with a 0.5 - 1 MWe turbine.

Excluding civil and structural works, the total investment cost for the equipment is USD 1,150,000. Based on the consumption and price of fuel oil, the annual savings in fuel oil purchases are expected to be USD 250,000. Moreover, annual savings from the disposal of residues is estimated at USD 13,000. An additional income to the company could come from the sales of ash, which are expected to generate a yearly profit of USD 179,000. The expected payback period of the plant is around 3 years after commissioning.

This husk contains about 75 % organic volatile matter and the balance 25 % of the weight of this husk is converted into ash during the firing process to supply energy and generate electricity, is known as rice husk ash (RHA). This RHA in turn contains around 85 % - 90 % amorphous silica. So for every 1,000 kg of paddy milled, about 220 kg (22 %) of husk is produced, and when this husk is burnt in the boilers, about 55 kg (25 %) of RHA is generated. Essentially, the high commercial value of the RHA may provide added incentive to venture into cogeneration in additional to the heat and power.

For further details log on website :
http://www.sarawakenergy.com.my/index.php/r-d/biomass-energy/paddy-residues-potential

Other Biomass Resources

There are other biomass resources potentially available for biomass source in Sarawak such as landfill gas, sewage sludge, and some agricultural wastes such as cocoa husk and sago wastewater.

LANDFILL GAS OF BIOMASS
Municipal solid waste (MSW) can be directly combusted in waste-to-energy facilities as a fuel with minimal processing, known as mass burn; it can undergo moderate to extensive processing before being directly combusted as refuse-derived fuel (RDF); or it can be gasified using pyrolysis or thermal gasification techniques. Each of these technologies presents the opportunity for both electricity production as well as an alternative to land filling or composting the MSW. Another MSW-to-electricity technology, landfill gas recovery, permits electricity production from existing landfills via the natural degradation of MSW by anaerobic fermentation (digestion) into landfill gas.

In contrast with some countries that have constrain to require lands for landfills purpose, "landfilling" could be an effective method for disposal of municipal and household solid wastes or refuses in the state since there are enough landfill areas can be provided in the state for landfill purpose. Although maintained in an oxygen-free environment and relatively dry conditions, landfill waste produces significant amounts of landfill gas, mostly methane. With the whole state of Sarawak dumping about 2,000 tons of waste per day, the total amount of landfill gases could be produced in Sarawak is estimated only about 2.3 MW.

Landfill gas (LFG) is generated by the natural degradation of MSW by anaerobic (without oxygen) microorganisms. The following Table shows the composition of landfill gas (LFG) obtained in average value by Department of Environment (1989).

Component	Composition (% by volume)
	Average in UK	Typical value in Malaysia
Methane	63.8	45 - 60
Carbon Dioxide	33.6	40 - 60
Nitrogen	2.4	2 - 5
Oxygen	0.16	0.1 - 1.0
Hydrogen	0.05	0.0 - 0.2
Ethane	0.018	-
Unsaturated Hydrocarbons	0.009	-
Acetaldehyde	0.005	-
Ethane	0.005	-
Butanes	0.003	-
Propane	0.002	-
Carbon Monoxide	0.001	0.0 - 0.2
Helium	0.00005	-
Halogenated Compounds	0.00002	-
Alcohols	0.00001	-
Higher Alkanes	<0.05	-
Sulphides, disulphides, mercaptans	0.00001	0 - 1.0
Others	0.00005	0.01 - 0.6

Table: Landfill Gas Component Analysis

Once the gas is produced, the gas can be collected by a collection system, which typically consists of a series of wells drilled into the landfill and connected by a plastic piping system. The gas entering the gas collection system is saturated with water, and that water must be removed prior to further processing. The typical dry composition of the low-Btu gas is 57 % methane, 42 % carbon dioxide, 0.5 % nitrogen, 0.2 % hydrogen, and 0.2 % oxygen. In addition, a significant number of other compounds are found in trace quantities. These include alkanes, aromatics, chlorocarbons, oxygenated compounds, other hydrocarbons and sulfur dioxide. After dewatering, the LFG can be used directly in reciprocating engines.

It can also be further processed into a higher-British thermal unit (Btu) gas (suitable for use in boilers for manufacturing processes, as well as for electricity generation via gas turbines.) The gas is also suitable for electricity generation applications such as gas turbines and fuel cells. Figure below simplifies the treatment of LFG before being used to generate electricity. The power generation method is optional whether to use steam turbine or gas engine.

Figure: Single line diagram of production of electricity from landfill gas

Table A below shows the rate of waste generation per capita in each division according to NREB (2007). The average rate is 1.19 kg/ca/d. Table B shows the prediction of power potential that can be obtained from LFG based on some data from Trienekens. They claimed that their landfill in Mambong Landfill releases LFG and the volume is gradually increase over the time. The highest forecast volumetric flow rate is 800 m3 LFG/hr. Besides, they also claimed that the calorific value of the gases is 25 MJ/m3. As a comparison, the last column represents the power potential if methane is extracted from the LFG in which the composition of methane is assumed as 55 % and the calorific value is 36 MJ/m3. To put in the nutshell, utilizing the LFG directly into gas engine has higher power potential compared to that of utilizing methane from LFG because of the volume is higher.

Division	Waste Capacity (ton/d)	Population (person)	Generation Rate (kg/ca/d)
Kuching	496.0	632,679	0.78
Samarahan	190.0	37,775	5.03
Sri Aman	88.0	17,100	5.15
Betong	65.0	57,000	1.14
Sarikei	94.0	45,500	2.07
Sibu	260.0	269,045	0.97
Mukah	66.0	53,983	1.22
Kapit	40.0	25,000	1.60
Bintulu	433.0	204,167	2.12
Miri	206.2	281,120	0.73
Limbang	50.0	52,959	0.94
TOTAL	1988.2	1,676,328	1.19

Table A: Waste generation rate in the State

Volumetric Flow Rate (m3 LFG/hr)	Potential Power (MW)
	Using LFGivision	Using Extracted CH4
100	0.69	0.55
200	1.39	1.10
300	2.08	1.65
400	2.78	2.20
500	3.47	2.75
600	4.17	3.30
700	4.86	3.85
800	5.56	4.40

Table B: Potential power output

 
According to NREB (2007), Mambong Landfill site received 450 ton/d, and according to Trienekens their landfill is currently generate more than 200 m3/h of LFG. By assuming these are true for this current state, 1 ton/d of solid waste could generate 0.444 m3 LFG/h and prediction for power potential for each division is made in the following Table.

By taking the lowest engine efficiency of 38 %, the total power potential in Sarawak is 2.3 MW but Trienekens claimed that there are 10 MW power potential from all waste in Sarawak. This may be due to the technology they are using has higher efficiency than 38 %. The power potential from LFG is still unattractive but the state can improve the solid waste management for future utilization of such green technology. However, developers should see this path as environmental perspective instead of investment return.

Division	Volumetric Flow Rate (m3 LFG/hr)	Potentia Power (kW)	Potential Electricity, 38% efficiency (kW)
Kuching	220.2	1529.3	581
Samarahan	84.4	585.8	223
Sri Aman	39.1	271.3	103
Betong	28.9	200.4	76
Sarikei	41.7	289.8	110
Sibu	115.4	801.7	305
Mukah	29.3	203.5	77
Kapit	17.8	123.3	47
Bintulu	192.3	1335.1	507
Miri	91.6	635.8	242
Limbang	22.2	154.2	59
TOTAL	882.8	6130.3	2330

Table: Potential power output in the State

SEWAGE SLUDGE

Sewage sludge in Sarawak can be classified into black water that came from the toilets, and grey water that came from wash areas like the kitchens. Grey water is disposed into drains that will eventually reached the rivers while the black water treatment involves primary treatment in septic tank, screening chamber, sedimentation tanks and aeration tank before released to the rivers.

There are three sewerage treatment plants in Sarawak located in Kuching, Miri and Sibu. The current treatment system of sewage sludge in Sarawak is illustrated in the following figure.

Figure: Current sewage sludge treatment in Sarawak

The deterioration of river pollution in Sarawak as being indicated by Malaysian Surface Water Quality in the following Table shows that the current sewage treatment is inefficient and requires a better and more organized system. One of the problems in the system is septic tanks. Tankers will only collect the sludge in the septic tanks once in 4 years or when requested by owners which means the treatment is not fully continuous. The untreated sludge that overflows between the collection periods is released to drains which will eventually be sent to rivers. This bypass occurred severely in the system especially for the undersized septic tanks.

Location	Physio-chemical	Bacteriological
Sg Sarawak Kanan	IIA/IIB	-
Sg Sarawak Kiri	IIA/IIB	-
Batu-Kawa Satok	IIA/IIB	III (Polluted)
Satok-downstream Barrage	III (Polluted)	V (Very Polluted)
Tributaries in Kuching	IV/V (Very Polluted)	V (Very Polluted)

Table: Sarawak Water Quality Classification

It is claimed that until 2008, there are 338,671 numbers of septic tank located in Sarawak that occupies for 182,374 Population Equivalent (PE) where 1 PE is equivalent to the capacity of 5 houses. Sewage treatment plant in Matang, Kuching receive 44 m3/day of sewage sludge from tankers collection. This capacity is not capable of treating sewage sludge in the whole region. Thus, Sewerage Services Department Sarawak is proposing a centralized sewerage system for the state to mitigate the problems of existing treatment system. The new concept is visualized in Figure below. This system channels both black and grey water into treatment plant through a network underground pipes and sewers. Wastewater is treated to Grad A before being discharged into the rivers.

Figure: Proposed centralized sewerage system

The sources of sewage sludge can be the residual semi-solid material left from industrial or wastewater treatment process and storm water flowing in drainage system. 75 – 90 % of the weight is water in which make it inefficient and not economical to convert to electricity. However, some technology has been used by different countries to utilize sewage sludge effectively, as shown in following Table.

Country	Method	End-product	Drawback
New Zealand	Alga is grown in sewage treatment process.	Biodiesel to energy	Time consuming
California, USA	Digested sludge is exposed to extreme heat and pressure so the cellular structures of solid are ruptured and easy to gasify.	Biosolid to energy	High operational cost due to high temperature and pressure
Lulu Island, UAE	Biogas from anaerobic digester is used in micro-turbines and fuel cells.	Biogas to electricity	-
United Kingdom	Heat from gasification of digested sludge is used to dry the sewage sludge before it can be gasified.	Biogas to electricity	-
Canada	Uses pyrolysis instead of gasification.	Biofuel to energy	-
Japan	Uses ultrasonic pre-treatment on the sludge so that solid present became more soluble. Ozone reforming refractory is used to reduce sludge volume and increase digestion gas production in methane fermentation. Sewage sludge is combined with garbage and other biomass.	Biogas to electricity	High installation cost of ultrasonic and ozone process
Illinois, USA	Combined anaerobic digestion and gasification process to optimize biogas recovery.	Biogas to electricity	-

Table: Methods of utilizing sewage sludge in different places

Figure below shows a concept of biological and chemical technologies combination to convert sewage sludge into electricity. Depending on composition of sewage sludge, the anaerobic digestion process will degrade 40 – 60 % by weight of the carbonaceous material which produces biogas of 65 % methane and 35 % carbon dioxide. The digested sludge can be dried out using conventional dryer or filter press to reduce the water content to 10 – 20 % before it can be gasified. Gasification at 1,700 - 2,800 o F can produce syngas of this constituent:

Carbon Monoxide	13 – 25 %
Hydrogen	10 – 28 %
Carbon Dioxide	8 – 17 %
Nitrogen	2 – 55 %
Water Vapor	11 – 41 %

 

 

Figure: Conceptual diagram of digester-gasifier hybrid system

COCOA AND SAGO

90 % of the cocoa pod weight is left as pulp, mucilage, sweatings and husk. Both pulp and mucilage are used for food and beverage production such as juice and jam while sweatings is used in acetic acid, ester and alcohol production. This makes only cocoa husk an available biomass from cocoa processing, which weights ten times that of cocoa bean. For sago which is the 3rd important agriculture product in Sarawak, the wastewater of sago processing plant can be used to generate electricity. Approximately, 5 m3 of wastewater is generated for the procession of 1 tonne of sago. Other waste of sago, which is coarse and fine hampas from starch extraction process, is not appropriate for electricity generation as it is more viable for synthetic polymer production. The usage of sago starch itself also does not appropriate because of the rising price of food worldwide. The potential energy that can be derived from these wastes is shown as per following Table.

Biomass	Production Rate	Moisture Content (%)	Lower Heating Value (kJ/kg)	Energy Available (GJ)
Cocoa Cocoa Husk	18,600 tpa	9	13,000	240
Sago Sago Wastewater	200,000 m3/annum	95	22	11.1

Table: Potential energy available from cocoa and sago waste

It can be seen that cocoa husk has slightly lower LHV compared to rice husk but higher than some of POB like EFB and fiber. However the potential energy is low because of the low production rate which made it less favorable for investors to utilize this biomass as electricity source. The same situation falls for sago wastewater where the production rate is much lower if compared to POME though LHV is identical.

ALGAE

Micro algae have a very fast specific growth rate as compared to other photosynthetic organisms. Like other plants, they use photosynthesis to harness sunlight and carbon dioxide. Energy is stored inside the cell as lipids (the source for oil) and carbohydrates. Algae can be converted into biodiesel, ethanol, biocrude and aviation fuels. Tailored algae within a highly controlled environment and fermentation of biomass can also be used to produce hydrogen. In some approaches, energy, food, and pharmaceuticals can be produced simultaneously. Microalgae have been demonstrated to capture over 80 percent of the daytime CO2 emissions from power plants and can be used to produce up to 10,000 gallons of liquid fuel per acre per year.
Among biofuels projects, algae are commonly grown in two scenarios; in ponds and in translucent containers called photobioreactors. In both cases the growth of algae requires a source of carbon, light, nutrients, and warm water. The ability to ingest CO2 and produce oxygen through photosynthesis is particularly attractive as a means to curb carbon emissions . The high cost of algae production remains an obstacle. The major conclusion is that there is little prospect for any alternatives to the open pond designs, given the low cost requirements associated with fuel production. The factors that most influence cost are biological, and not engineering-related. These analyses point to the need for highly productive organisms capable of near-theoretical levels of conversion of sunlight to biomass. Even with aggressive assumptions about biological productivity, the costs for biodiesel were projected two times higher than current petroleum diesel fuel costs.

There are efforts made to establish the feasibility of large-scale algae production in open pond systems. Study proved that outdoor ponds could be run with extremely high efficiency of CO2 utilization. Careful control of pH and other physical conditions for introducing CO2 into the ponds allowed greater than 90% utilization of injected CO2. Of essential concerns are ways to achieve consistently high productivities with conducive conditions at the site, ample sunlight and right temperature.
Cultivation methods for microalgae in open ponds have been developed to a point where media specification and unit designs are fairly standard, but there remain many technical, engineering and economic questions that stand between the desired productivity and the present available data to produce algal biofuels.

Tremendous advances were made in the science of manipulating the metabolism of algae and the engineering of microalgae algae production systems; particularly in the production of biodiesel from high lipid content algae grown in the ponds, utilizing CO2 emission from coal fired power plant.

Carbon capture and displacement fossil fuels are likely the roles for growing algae to produce oil. Many industries are seeking to develop costly and elaborate technologies and system to capture, concentrate and sequester CO2 generated in fossil fuel power plant in the earth or in the oceans. In fact algae can perform an equivalent sequestration by utilizing captured and using sunlight as the source of energy.

Commercialization to produce specialty chemical products is well advanced (nutritional supplements, primarily spirulina (Arthrospira plateasis). However, commercialization to produce high volume biofuels faces extensive challenges with regard to biological, engineering and economic factors.
The fact of the matter, the estimated capital cost (excluding operation cost) could not be justified with a currently achievable yield of oil content biomass for biodiesel. Thus, this requires a major productivity improvement of such systems and increases tremendously the outputs of what is currently possible. The possible pathway is to envisage the possibilities in succeeding commercial scale of biofuels production via microalgae together with the value chain as income streams to support and make it viable such as co-production of higher value specialty products and carbon capture monetization.

Hence, as present, we shall keep abreast with the development and emergence of promising technology, significant genetic breakthrough and economic viability so that we will be able to grasp these advantages to curtail carbon emission in future as well as an absolute option to produce sustainable biofuels, particularly for biodiesel.

For further details log on website :
http://www.sarawakenergy.com.my/index.php/r-d/biomass-energy/other-biomass-resources