Increasing diesel prices, stricter emission norms and toxic pollution in urban cities have compelled governments and school transport authorities to look for cleaner and greener alternative fuels.
These must not only help to safe guard the health of school going children, but also pass the test of viability and cost effectiveness.
Here is a look at the pros and cons of various alternative fuels:
1.Clean Diesel (ULSD):
This is ultra-low Sulphur diesel which ranges from 300 ppm to 50 ppm. Most countries have already mandated the move to ULSD for all diesel vehicles, including the school buses.
ULSD has the highest energy density among the transportation fuels.
Sulphur is up to 97% less, so extent of soot pollution greatly reduces.
The upgraded engine is smoother and more efficient.
Various after-treatment components – DOC, DPF, SCR, EGR and DEF enable the filtration of particulate matter and oxidation of exhaust gas components, further reducing the harmful emissions.
Too many emission reduction components are required, which increases complexity.
Upfront costs as well as maintenance costs for all the components are high.
While GHG emissions are significantly lowered, NOx levels do not reduce sufficiently, hence health risk to children still exists.
This is natural gas (primarily methane) compressed to less than 1% of its original volume.
It has been acknowledged worldwide as a viable option, particularly in Asia-Pacific and Latin American countries.
In India, there has been a rapid increase in distribution and fueling infrastructure for CNG, and the goal is to reach 10,000 fueling stations in the next 10 years.
It is the cleanest fossil fuel, leaves very little residue on pipes and tubes, and does not contaminate motor oil, so requires much less maintenance.
Emits much less harmful compounds versus diesel and gasoline.
Has high ignition temperature and is lighter than air, so the risk of fire is reduced.
High infrastructural costs makes it difficult for transport companies to recoup their investments, without the help of government bodies.
As compared to filter equipped ULSD buses, the buses running on CNG have lower NOx emissions, but slightly higher hydro carbon and particulate matter emissions.
Requires more storage space as compared to a liquid fuel.
It is a fossil fuel, not a renewable fuel, so may run short in the longer run.
This is raw biogas, upgraded to Bio CNG by increasing the concentration of Methane and removing other compounds. It has been generating a lot of interest worldwide as a viable transportation fuel.
In India, there are 17 manufacturing plants for Bio CNG and more on the anvil.
Occurs abundantly in its raw form and is 100% renewable.
It is a low-cost fuel, about 25%-50% lower than diesel
Reduction in GHG is as much as 90%
In spite of its obvious advantages, there is not much awareness and less implementation till date.
This is the most promising alt-fuel technology, and most countries have been developing and implementing various prototype versions over the last few decades.
The UAE for instance, has mandated 30% of all vehicles to go electric by 2030.
The batteries are specially designed to withstand high heat conditions.
About 300 e-school buses are slated to ply in the UAE in the next couple of years, going up to 1000 e-school buses by 2023.
Zero tailpipe emissions, quieter operations, lower maintenance costs
Lower fuel cost, leading to low cost of operations in the long term
Ideally suited for school buses, since they ply on fixed routes, so longer battery life and improved mileage can be expected.
The cost of acquiring electric school buses is currently prohibitive, unless the government steps in with grants, incentives and low interest loans.
At the current level of development of the batteries, the distance range is 50-130 miles.
Depending on weather conditions in a country, the e-school buses will either need air conditioning or internal heating, for which they would have to rely on fossil fuels, otherwise the battery would be depleted.
E-school buses may not be as clean as they seem, because a lot depends on the source of electricity – for many countries, this is primarily fossil fuel.
5.Hybrid Electric: This technology comprises a combination of energy conversion technologies (heat engines, generators, motors etc.) and energy storage technologies (fuel, batteries etc.).
The conventional and electric propulsion systems work together to bring in more efficiency
They are at least twice as much more fuel efficient, have lower emission than diesel buses, and longer distance range as compared to the electric buses.
Refuelling is easy and rapid, as it makes use of existing fuel stations.
The buses can also run on alternative fuels in future.
The technology is still in its development stage, so no disadvantages have been seen yet.
Propane (LPG): LPG is obtained as a by-product of natural gas processing or crude oil refining, and comprises primarily of propane. Many countries have recognized this as a very viable alternative fuel for the school buses.
In the US, over 15,000 school buses are successfully running on LPG.
It has a lower carbon to hydrogen ratio, higher octane, forming a homogenous mixture in the combustion chamber, which greatly reduces emission levels on all counts.
Build up on engine parts is very less, reducing maintenance costs and increasing the service life of the vehicle.
The fuel is very volatile hence proper standards with regards to safety, storage and handling needs to be communicated and followed.
In conclusion, even though the future of school buses looks exciting, with many promising fuels on the horizon, switching to the right fuel would require careful consideration of cost versus benefits.
In the meanwhile, a school bus tracking system with real time route optimization, driver behavior monitoring and live vehicle emission tracking will continue to help you reduce fuel costs and emissions, ensuring you extract the best possible efficiencies out of your existing fleet.