Biodiesel: A renewable fuel synthesised from crop oil such as that of Rapeseed, Sunflowers and Soybeans, but waste cooking oils can also be used to produce it. This means you can make your own. You'll be just like Walt from Breaking Bad! Just watch out for those poisonous fumes. Biodiesel produces significantly less CO2 emissions that regular Diesel, however; it can produce higher Oxides of Nitrogen (Smog to you and I) than some types of Diesel. Cars often run on a blend of Bio and conventional Diesel though some can use a 100% mix. Biodiesel is the most widely available Bio-fuel in the UK and, according to Uk Energy Saving, by 2013 all Diesel cars in the UK will be configured to run on Biodiesel.

Bioethanol:  It's Alcohol, but don't be mixing it with ginger ale, ice and lime. It's typically produced from Sugarcane, Cereal Crops or Sugarbeet. Bioethanol is safe for use in modified petrol engines or FFV's (Fuel Flex Vehicles). Again, this stuff is renewable and, predictably, is better for the environment than both petrol and diesel. There are downsides of course. Bioethanol filling stations are currently few and far between. Also, you're going to have to pay more for the privilege of owning a car that can run on this renewable. There are also potential drawbacks to mass growing crops for its production but we're sure somebody's working on that right now.

Biogas:  One of the most effective (and disgusting) alternatives to Petrol and Diesel. A mix of mainly Methane and Carbon Dioxide, the two main methods of getting hold of Biogas are: extracting it from landfill sites, or, something called Anaerobic Digestion, which sounds like the name of a Death Metal band. Either way it involves dealing with either decomposing rubbish or sewage, so as we said, disgusting. On paper, Biogas sounds great: 60% reduction on CO2 compared to Diesel (approx), lower Nitrous Oxide emissions and negligible particulate emissions. In practice, at time of writing there are no manufacturers producing Biogas friendly cars for the UK.

Fuel Cell:  The brainchild of one Sir William Grove in 1839. Yes, 1839. These cells are typically used by people like NASA, rather than people like Ford. However, that could all be set to change as there are a great many environmental benefits to be gleaned from using such a method to power a car; the only admissions being heat and water vapour! Trouble is that it is all very costly and the UK is yet to develop a means of widespread refuelling.

LPG: LPG stands for Liquid Petroleum Gas and can offer a significant reduction in emissions. LPG can offer a 10% reduction on CO2 compared to petrol and a whopping 80% reduced Nitrogen output when compared to Diesel engines. Disappointingly, the CO2 compared to Diesel is 10% higher but you can't have it all (unless you've got a Hydrogen fuelled rocket car, obviously). You can convert your car to run on LPG for a not insignificant fee (£1500 approx), or simply arrange for your new car to be converted upon purchase. A handy guide to conversion can be found here. 

Natural Gas:  This stuff is usually used for cooking, however it can be stored under pressure and can then power vehicles. Typically, Natural Gas is being used to power larger vehicles such as HGVs, buses etc. There are a variety of different advantages to using natural gas as a fuel, including: reduction in engine noise, reduction in emissions and if you're in London, you'll be exempt from that pesky congestion charge! Hopefully we'll see this getting used more for smaller vehicles in the near future then.

Pure Plant Oil:  Pure plant oil is made, perhaps unsurprisingly, by crushing plants. It was first utilised, very surprisingly, by a chap called Rudolf Diesel in 1912. His first ever engine was able to run on peanut oil. Again, not widely used in the UK, pure plant oil reduces some emissions. However, it is thought that overall emissions are largely the same as when using traditionally fuelling methods. The UK also has no refuelling network for Pure Plant Oil, although it is widely used in European countries like Germany.

Image courtesy of: Sean.