3 replies to this topic

I find it misleading since whatever the case is, biofuels will eventually pay back the carbon debt as opposed to using conventional fuels where you can repay the debt at all..

[NeiNastran]

To answer the question of this topic: Yes, biofuels contribute to greenhouse emissions. Any fuel that is burned will produce C02 as a byproduct of combustion. However, from what I know about biofuels, they tend to burn a lot cleaner (probably not producing as much N0x as fossil fuels). I'm not sure if they produce less C02 as fossil fuels - but they definitely appear to be a step in the right direction. Have you seen that new National Geographic about biofuels? I was impressed with the Algae case - I would like to learn more about that.

[TroyH]

It's a complicated question, and the answer to it depends on the source of the fuel.

The two most common biofuels today are ethanol and biodiesel. Ethanol can be sourced from many feedstocks, but wheat, sugarcane and corn are probably the most widely used feedstocks.
All of these will have associated emissions from harvesting and processing (which can potentially be eliminated/reduced if the power/fuel is sourced from non-fossil fuel sources.)
There are also some emissions associated with growing. In the case of corn and wheat, there are fertilisers, and pesticides etc, which are often sourced in part, from fossil fuels (for example: ammonium nitrate fertiliser).

I'm not sure on the cultivation techniques employed for sugar cane, but for all three sources, there is the possibility of competition for land use, resulting in land being cleared somewhere in the world to make up for the shortfall in whatever crop was replaced by the biofuel crop (which is also a major criticism of biodiesel made from plant oils). I'm not convinced that there is a direct acre for acre relationship (because surely increased prices leads to reduced demand?) but it seems the evidence supports the fact there is a problem.

Biodiesel is usually made from plant oils or waste plant oils/animal fat. As stated earlier, the emissions associated with these, are much the same as those for ethanol crops.

There is also emissions associated with production of the fuel itself. The process equipment usually required heat and electricity, which has to come from somewhere. More often than not you will find fossil fuels as the source for this energy. Once again, if you replace these sources with renewable sources, then you eliminate the emissions from this.

Lastly, most biodiesel is made using methanol. Most of the methanol is made from hydrocarbon fuels. So there are emissions associated with this.

I would very much doubt that there is any biofuel on the market that could be called "carbon neutral", which I would define as having had no net effect on the amount of carbon in the living carbon cycle, when examined over the lifetime of the product.

That said, we have to start somewhere. Opening up the market to biofuels means that more money is spent investigating better, cleaner methods of productions. This trend is evident by the number of large oil and gas companies who are investing in research in this area (BP, Shell, Technip and ConocoPhillips to name a few).

There are a number of technologies around that together have the potential to significantly reduce (if not eliminate) greenhouse emissions, and provide sustainable sources of biofuels.

It is a very interesting field, but seems to be riddled with misinformation, skepticism and arguments from people not able to see the bigger picture.

My 2c.

[Thushara]

Answers to TroyH

"There are also some emissions associated with growing. In the case of corn and wheat, there are fertilisers, and pesticides etc, which are often sourced in part, from fossil fuels (for example: ammonium nitrate fertiliser)."

We can use organic fertilizer such as compost and biogas generators sludge as good source of fertilizers. This is environmentally and financially viable solution.

But when we are doing our bioethanol or biodiesel project in large scale this will be very not easy process. But I think this is a better solution for pilot scale projects, small scale industries even for medium scale.


I'm not sure on the cultivation techniques employed for sugar cane

I have visited sri lanka's largest sugar industry, Pelwatta Suger Industries and it uses more than 15000 hectares for cultivation. Actually sugar cultivation need very lager extensions of lands. We can user sugar cane for directly as food processing raw material and we can use residues to make ethanol or as biomass fuel for combine heat and power plants.

"Most of the methanol is made from hydrocarbon fuels. So there are emissions associated with this."

But we can produce methanol from waste such as saw dust. In my university, in my engineering department some of my friends are doing final year project for designing a process to manufacture methanol from saw dust.