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According to a chart posted in a Skeptics question, biodiesel is the worst energy source we have in terms of return on investment:

roi energy

However, every time I travel outside the city in Europe I see huge fields of rapeseed and I know that biodiesel is heavily subsidized by the EU. So what's the rationale for investing so much in such a horrible power source? Are there plans to abandon the project and switch to more efficient sources of alternative energy?

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    Was going to comment on value of renewable sources beyond ROI, but then noted the specific "more efficient sources of alternative energy" part of your question. Just noting it here in case people miss it like I initially did. – PoloHoleSet Jun 1 '17 at 16:10
  • The way ROI is measured here doesn't seem to warrant the choosing of one solution over the other. In that they all produce a return would seem to indicate there's no reason one couldn't invest in all of them and see where advances get us. – user1530 Jun 1 '17 at 20:11
  • @blip logic dictates one would invest the most into hydro, then into wind, then into solar. And if you still have money, invest into rapeseed. – JonathanReez Supports Monica Jun 1 '17 at 20:32
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    @JonathanReez only if these technologies were all extremely mature. There's plenty of good arguments to continue investing in immature technologies to see where they get us in the future. (ie, R&D can be a valid investment) – user1530 Jun 1 '17 at 20:38
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    @JonathanReez we're getting into really broad topics here. You're not wrong, but at the same time, industries and economies of scale also drive the speed of R&D. There's a lot of variables and nuances here that could be explored. – user1530 Jun 1 '17 at 21:14
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It still has a positive ROI, so that doesn't seem like a fair reason to abandon it. Just looking at the ROI, there should be no reason to use nuclear or natural gas, as hydro and coal have a far better ROI.

Biodiesel is one of the few renewable energy sources which can be used in cars, trains, ships, and planes without too much adaption of the existing machinery, and without a need for a severe change in infrastructure (electric cars for example cannot be recharged at a normal gas station). Biodiesel also doesn't have the downside of e.g. electric cars (low reach, etc).

But yes, there are plans to abandon or at least adapt the approach to biodiesel - mainly because of the ecological and social downsides of it. The current approach seems to be to move to advanced biofuels which do not have these downsides (but require more investment and research before they become viable on a large scale).

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    @blip The graph from the OP is specifically about EROI (energy returned on energy invested). It's not about financial ROI, and it doesn't take any other factors into consideration (environmental, social, etc). – tim Jun 1 '17 at 20:47
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    "It still has a positive ROI" everything has, it's a ratio of 2 positive numbers. the point should about wether it is >1 or not – Federico Jun 2 '17 at 16:17
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    @Federico "positive ROI" in this case obviously means "more return than investment", ie ROI > 1. This is also how the phrase "positive ROI" is used in practice. The point is, biodiesel doesn't result in a net energy loss. – tim Jun 2 '17 at 16:28
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    Maybe I'm a little bit too mathematician inside, but personally I'm not convinced by how it is used in practice. (I've not downvoted btw) – Federico Jun 2 '17 at 16:34
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    +1: for use without extensive adaptation of existing infrastructure – Mozibur Ullah Aug 7 '17 at 5:57
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Energy return on investment (EROI) isn't a useful measurement. Hydro power tops your table, but hydro is only 6.5% of US power generation. Natural gas is a leading power source, despite being very average in EROI.

If there is one meaningful limited resource, it's money. Governments use a metric called levelised cost of electricity. This is a better metric because it accounts for all inputs (energy, labour, capital) all of which are limited.LCOE

Even this metric is lacking. Energy sources have many diverse factors which make them good or bad. Bio diesel produces a high-density highly-compatible liquid fuel, low carbon, is relatively low in air pollution, highly storable and domestically producible. None of these features are accounted by EROI, and most of these aren't accounted for by simple economic analysis.

Because most of the benefits are non-market, either environmental, political or geopolitical benefits, governments subsidise bio-diesel. Whether it's good for the country will require a detailed look at all costs/benefits, not just EROI.

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