FUEL
Pakistan’s current estimated population is 185 million and it is expected to double in the next 36 years. The country’s energy demand is about 120 MTOE (million tons of oil equivalent), while the current supply is 99 MTOE with a shortfall of 21 MTOE. The current estimated oil import is around 346,400 barrels/day (with the current approximate price of crude oil at $30/ barrel) and the total petro-diesel consumption in the country is around 8.22 million tonnes per year. The major portion of energy demand is met by fossil fuels, which are non-renewable resources and the major source of greenhouse gas emissions, creating climate change/global warming issues in the world. This resource is also finite and would not last for more than 50 years.
Sustainable development in the renewable energy sector is necessary to reduce dependence on imported fossil fuels. This will not only save valuable foreign exchange reserves but also mitigate climate change and global warming issues.
The importance of alternative renewable environment friendly biodiesel fuel has been realised in the last few decades in Pakistan. The non-edible vegetable seed crops such as: jatropha (rattan joot), pongamia (sukh chan), castor (arand) and eruca sativa (tara mera), are the potentially suitable crops that can be cultivated on marginal land, with regard to the favourable climatic conditions of Pakistan for its growth with less water consumption as compared to edible vegetable seed crops.
The approximate oil content present in jatropha seed is 37 percent, pongamia 30 percent, castor 40 percent and eruca sativa 35 percent. The maximum oil yield from jatropha, pongamia, castor and eruca sativa is 1,892, 1,430, 1,413 and 1,750 litres per hectare per year respectively.
For economic stability and sustainable development in the country, government incentives and subsidy would encourage the farmers to get their earnings and create job opportunities based on utilising their idle non-arable land productively (approximately marginal land in Pakistan - 350,000 acres).
It was observed that planting 1,000 saplings of jatropha in one hectare, yields around 1.5 tonnes of seeds per year. It is expected to create one job for each four hectares of cultivation of non-edible crops on marginal land. The jatropha seeds and its extracted oil prices are approximately Rs6/kg and Rs26/ kg respectively.
The total production cost of biodiesel from this source is between Rs80 to Rs100 per litre, which is not competitive with petro diesel (Rs75.66 per litre), requiring measures to reduce its production cost. The foresight shows that renewable biodiesels are the everlasting source of transportation fuel as compared to fossil fuels. Its production cost can be reduced by for example: using its by-product crude glycerol (market value $1.5/kg or Rs105/kg) as raw material in pharmaceutical, cosmetics, soap manufacturing and for the production of hydrogen fuel.
Converting the de-oiled vegetable cake into bio-methane gas, and using solar heat energy for the processes to produce biodiesel can also bring its cost down.
The oil from jatropha vegetable seeds is extracted with a simple mechanical expeller and can be converted into liquid biodiesel fuel for the transportation sector, while its de-oiled cake can be transformed into gaseous bio-methane fuel (biogas) for heating and cooking purposes with an anaerobic fermentation process in a closed reactor, which also helps to bring down the cost of biodiesel.
Biodiesel is used in existing diesel engines without any modifications. It is a cleaner burning fuel and is produced with a chemical reaction of vegetable oil with an alcohol (methyl alcohol) and a base catalyst (caustic soda), while glycerol is recovered as a by-product (for every 4 litres of biodiesel produced, 0.45kgs of glycerol generated). The most optimum blended biodiesel (jatropha 20 percent + petro diesel 80 percent by volume) has no adverse effect on engine components; it emits 20 percent less carbon dioxide and 50 percent particulate matter into the atmosphere.
While the power (kW) generated by the engine running on biodiesel is lower with values between five to seven percent as compared to petro diesel, this value can be compromised in terms of mitigating environmental degradation. Unfortunately, 100 percent biodiesel cannot be used in automobiles due to its high organic solvent property, which clogs the fuel injection system.
Table below shows a simplified field to supply chain mass balance, excluding production consumables such as energy or transport of the process. The vegetable oil deed grown by farmers is crushed to recover crude seed oil with the useful by-product ie de-oiled cake. The resultant extracted crude vegetable oil, along with alcohol (methyl alcohol) and catalyst (caustic soda), is then used as feedstock for the biodiesel production and the co-product glycerin. The methyl alcohol and the catalyst used for the conversion of vegetable oil into biodiesel are recovered and can be recycled. All values in the Table below are in tonnes (where 1 tonne = 1,000kgs).
Furthermore, in order to reduce the production cost of jatropha biodiesel, its de-oiled cake is converted into gaseous combustible fuel with a fermentation of biomass in a closed reactor in the absence of oxygen, converting the organic matter into bio-methane (biogas) for cooking/ heating, lighting and power generation purposes in domestic use. It offers a promising alternative route for converting biomass into bio-gas (whose major constituent is methane gas approximately 50-75 percent by volume) with energy value between 20-26 mega joules/cubic meter (whereas the natural methane gas having energy value of 40MJ/kg).
About 20kg of wet de-oiled biomass can produce one cubic meter of biogas/day which is approximately equivalent to generate 6kWh. The 6kWh power is sufficient energy to power three 100W incandescent bulbs for 20 hours. While the residue sludge after producing biogas is then used as a natural organic fertiliser rich in nitrogen, phosphorus and potassium for farming edible crops.
The Pakistan Council of Renewable Energy Technologies (PCRET) efforts are commendable which took an initiative to install five cubic meters capacity of biogas plants in rural areas of Pakistan. While the efforts of Alternative Energy Development Board (AEDB) are also laudable for initiating National Biodiesel Programme to replace 10 percent of the total diesel consumption with biodiesel by 2025.
The current daily import of 346,400 barrels/day of crude oil in the country produces 4,156,800 gallons/day petro-diesel (for every one barrel of crude oil approximately 12 gallons of petro diesel is produced). Using 10 percent blended biodiesel fuel with petro diesel will proportionally reduce the quantity of diesel consumption by 415,680 gallons/day (saving 34,640 barrels/day of imported crude oil ie $30/barrel, saving around $1,039,200/day).
Pakistan is blessed with a lot of natural resources and those can be utilised to bring economic and sustainable environmental stability in the country. Utilising marginal land to cultivate non-edible vegetable seed crops can give us oil to produce renewable biodiesel, which will reduce the oil import bill.
The writer is an Assistant Professor at NED University
INPUTS CRUSH PLANT BIODIESEL PRODUCTIONS OUTPUTS
Raw seeds from field 100 100 — —
Chemical reagents i.e.
Methyl alcohol + 4 — 4 —
catalyst (caustic soda)
Crude Vegetable oil — 43 43 —
De-oiled cake — 57 — 57
Biodiesel produced — — 43 43
Crude Glycerin — — 4 4
Outputs 104 — — 104
