# Waste to fuel...economic efficiency? **URL:** \ **Category:** Factual Questions\ **Created:** [April 22, 2008, 11:37pm UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474 "2008-04-22T23:37:40Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [April 22, 2008, 11:37pm UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/1 "2008-04-22T23:37:40Z")
Lets keep this discussion centered on diesel fuel, as it is the primary fuel of the engines that power the economy (ships, locomotives, 18-wheelers). Diesel is now at least $3.25 a gallon…and the price will only go up. Practical alternatives to petroleum are now not only desirable, but critical. Catalytic pyrolysis can make diesel from plastic. [http://www.polymerenergy.com/](http://www.polymerenergy.com/) Thermal Conversion makes diesel from biomass…like turkey guts. > **[Thermal depolymerization](https://en.wikipedia.org/wiki/Thermal_depolymerization)** > > Thermal depolymerization (TDP) is the process of converting a polymer into a monomer or a mixture of monomers, by predominantly thermal means. It may be catalysed or un-catalysed and is distinct from other forms of depolymerisation which may rely on the use of chemicals or biological action. This process is associated with an increase in entropy. > For most polymers thermal depolymerisation is chaotic process, giving a mixture of volatile compounds. Materials may be depolymerised in this way durin... Fischer-Tropsch process makes fuel from carbon monoxide and hydrogen > **[Fischer–Tropsch process](https://en.wikipedia.org/wiki/Fischer-Tropsch_process)** > > The Fischer–Tropsch process (FT) is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at temperatures of 150–300 °C (302–572 °F) and pressures of one to several tens of atmospheres. The Fischer–Tropsch process is an important reaction in both coal liquefaction and gas to liquids technology for producing liquid hydrocarbons. > In the usual impleme... Biodiesel is made from processing vegetable oils and/or animal fats with an alcohol and an alkali > **[Biodiesel](https://en.wikipedia.org/wiki/Biodiesel)** > > Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with an alcohol, producing a methyl, ethyl or propyl ester by the process of transesterification. > Unlike the vegetable and waste oils used to fuel converted diesel engines, biodiesel is a drop-in biofuel, meaning it is compatible with existing diesel engines and di... These four alternatives will be viable supplements to Petroleum derived diesel. Question is…_how_ viable? What are the hard numbers regarding the amount of raw feed stock, the return of energy investment, how much these processes can bring down the price of fuel? I already know that Biodiesel returns about 3.24 time the energy invested in its manufacture. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [April 23, 2008, 2:35am UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/2 "2008-04-23T02:35:47Z")
BTW, since sulfur has been taken out of diesel fuel for emissions, some substitute fuel lubricant must be used…and biodiesel is the best there is. Cheap, lubricating, and clean burning. With no sulfur, there is no production of toxic sulfuric acid vapor. Exhaust can be passed through a catalytic converter without problem. ---
**Author:** ![The\_Them](https://avatars.discourse-cdn.com/v4/letter/t/898d66/32.png) [@The\_Them](https://boards.straightdope.com/u/The_Them)\ **Post date:** [April 23, 2008, 7:23am UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/3 "2008-04-23T07:23:39Z")
Wiki is not always my favorite source, but this story seems to be unbiased. It more or less matches what I’ve heard occasionally mentioned on local news. Now, whether this Carthage turkey-waste plant is efficient enough to run without external fuel input for its hauling vehicles, utilities and the like…dunno. They sent me a recruiting (yeah, turkey waste=me, bring on the jokes) brochure a couple years ago, which came off as a little more optimistic than I thought _totally_ plausible. With petroleum prices as high as they’ve been, and improved methods… ---
**Author:** ![control-z](https://avatars.discourse-cdn.com/v4/letter/c/eada6e/32.png) [@control-z](https://boards.straightdope.com/u/control-z)\ **Post date:** [April 23, 2008, 6:02pm UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/4 "2008-04-23T18:02:12Z")
Isn’t diesel at least $ **4**.25? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 23, 2008, 6:37pm UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/5 "2008-04-23T18:37:34Z")
[QUOTE=control-z] Isn’t diesel at least $ **4**.25? [/QUOTE] Here is where I check for cheap Diesel: [Pilot Company | Travel Center & Gas Station Network](http://www.flyingj.com/fuel/diesel_CF.cfm?state=ALL) ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [April 23, 2008, 10:14pm UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/6 "2008-04-23T22:14:29Z")
[QUOTE=control-z] Isn’t diesel at least $ **4**.25? [/QUOTE] At a local gas station around where I live, diesel was $3.23 a gallon. Remember…waste plastic, waste biomass, waste deep-fryer grease…are resources that people WILL PAY YOU to take off their hands. I can imagine a few years from now, landfills being mined like a natural resource. ---
**Author:** ![Public\_Animal\_No.9](https://avatars.discourse-cdn.com/v4/letter/p/b9e5f3/32.png) [@Public\_Animal\_No.9](https://boards.straightdope.com/u/Public_Animal_No.9)\ **Post date:** [April 23, 2008, 11:41pm UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/7 "2008-04-23T23:41:45Z")
The “hard numbers” are rarely that when it comes to waste to fuel. There are a number of issues that make it difficult to make any blanket statements about waste-derived fuels. First, as you’ve pointed out, there are several approaches to converting the waste to useful fuel. Each of those will have its own ratio of total energy input to energy output in the fuel. One process that isn’t widely discussed is the conversion of bio-oils to a form that can be used in a conventional refinery to create conventional diesel fuel. Given that much of the production and distribution infrastructure is already in place, this approach has a lot of promise IMHO. The second factor, and one that is often overlooked, is that waste material has (relative to crude petroleum) a very low energy per unit collection area density. That is, waste materials must be collected from a broad geographical area to provide enough feedstock to make any significant fuel production facility economically viable. The collection process usually involves driving around and collecting the waste (or alternatively, having the waste drive by the waste generator to you, which is the same thing from an energy perspective). Third, the feedstocks are often closely linked to the price of oil because of the inherent oil content of the waste. Plastics are petroleum based, vegetable and animal oils are derived from agriculture which is highly dependent upon petroleum, and so on. So the price of the feedstock can fluctuate in the same way as oil, which reduces the overall price advantage of waste as a feedstock. See also point 2 above relative to the collection process. Finally, it’s critical to have a steady long-term supply of the waste, which is not easy to come by if you’re relying on something like restaurant grease (restaurants go out of business). If you’re sinking millions of dollars into a conversion plant, it’s not good if you suddenly can’t get enough feedstock to generate your product, even if others are paying you to take it away. And that practice won’t last long if waste becomes a commodity. Pretty soon people will see that they can charge to have people use it, and the economics will change substantially. Utilization of waste for fuel production is generally a good idea. But it’s not a panacea by any means. There are currently situations in which it makes sense and where it will be profitable and largely sustainable. But it’s not likely to be something that is always better all the time. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [April 24, 2008, 3:51am UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/8 "2008-04-24T03:51:41Z")
I believe outside New York City is a massive landfill which holds literally cubic miles of trash. Catalytic pyrolysis and Thermal Decomposition plants operating on site could provide a steady flow of diesel for decades. ---
**Author:** ![Tuckerfan](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tuckerfan](https://boards.straightdope.com/u/Tuckerfan)\ **Post date:** [April 24, 2008, 10:24am UTC](https://boards.straightdope.com/t/waste-to-fuel-economic-efficiency/446474/9 "2008-04-24T10:24:24Z")
[QUOTE=Enola Straight] I believe outside New York City is a massive landfill which holds literally cubic miles of trash. Catalytic pyrolysis and Thermal Decomposition plants operating on site could provide a steady flow of diesel for decades. [/QUOTE] So could hemp if it was processed into biodiesel, I don’t exactly see that happening in the States any time soon, ya know? There’s been threads on this process before and IIRC, the local experts have weighed in with the “it works in lab settings, but I’m not convinced it’s quite ready for prime time yet.”