Naked Science Forum
Non Life Sciences => Technology => Topic started by: another_someone on 11/03/2008 22:12:51
-
OK, this is maybe half tongue in cheek (don't ask which cheek). So you are all allowed to laugh at the absurdity of it all.
I was considering the idea of a low power grass cutter, feeding the cuttings into a methane digester, which then feeds its methane into fuel cells, and those fuel cells than charge up some batteries. While it is doing this, the composted waste could then be returned to the fields as fertiliser.
Then put this on 4 or 6 legs, and let it slowly roam around a field, and regularly return to some base station where it could offload the charge in its batteries.
OK, it almost certainly will never be cost effective (the amount of power it will generate will be very small compared to the capital cost of the machinery).
Besides that, what else won't work (apart from the fact that if you had a dozen of these in a large field, you'll probably find them loaded on the back of someone else's lorry in the dark of the night).
-
I like it.. George... That sounds like quite the machine!!!
I know some people who would miss the cow pie smell... or will this still accompany the machine as it fertilizes the fields!
-
Some ride on lawn mowers already have the technology to mulch the grass and return it to the field/lawn without smothering the fresh growth.
Legs will always be a problem especially on an uneven surface. The most successful robotic animals are more insect like in their leg movement as they are more stable. Wheels are a much better option.
I'm not sure how big the methane digester would have to be in order to power the thing never mind produce extra power. Does a methane digester work well on grass cuttings?
I do like the idea though, anything you can just leave and it works without intervention is good. More time for Pimms on the lawn.
If people are cattle rustling then you need a mechanical watch dog to bark at and bite any offenders.
-
That is why I allowed for 4 or 6 legs (could even go for 8 legs, with 4 down and 4 up at any one time)- as you say, insect style walking is more stable.
A number of reasons why I did not go for a wheeled option.
Wheels tend not to be good for the ground they go over. In particular, wheels are bad if they are standing still, whereas legs work better for standing, even if there is a penalty when they move. It is also much more difficult to get a wheeled vehicle just to move a short distance forward - the cost of starting the wheels rolling and then stopping is relatively high compared to the low cost of continuous motion.
Since the idea is that this electric cow wants to traverse the field at a speed so that it can consume the grass at a speed comparable to the speed at which the new grass will grow, it clearly is not looking to do a high speed sprint across the field, otherwise it will simply quickly consume all the grass in a short time, and be left with nothing to do while it digests that grass. If it only moves slowly, just topping up with a little grass at any one time, while the digester works on what it has already consumed some time ago, and the grass keeps growing to replace what has been consumed, the entire process can be kept in better balance. This is better done at walking pace than with a high speed roll over the lawn.
-
The mechanical cow could make better use of the energy it gathers than a real cow; it would be more like a reptile than a mammal as it would not need to keep itself warm. When conditions were not good it could just shut down, whereas a real cow has to keep itself alive. It would probably be even more efficient for the cow to deliver a partly 'digested' load to a central digester.
An alternative could be to grow crops on a conveyor belt or set of panels which could carry and dump the mature plants into an enormous, more efficient, digester. The system could possibly float on water which would minimise the cost of (very slow) transportation. A cycle would take many months. If it were to be built at sea, the energy for transportation could be provided by tide or wave.
The cow idea sounds more fun tho'.
-
The mechanical cow could make better use of the energy it gathers than a real cow; it would be more like a reptile than a mammal as it would not need to keep itself warm. When conditions were not good it could just shut down, whereas a real cow has to keep itself alive.
Indeed so.
It would probably be even more efficient for the cow to deliver a partly 'digested' load to a central digester.
Possibly. My main concern is that the methane digesters have to work in anaerobic conditions, and one has to ensure that the transfer process does not introduce air into the system (this should be possible), but one also has to be sure that nothing else in the transfer process would unsettle the digestion. Also, having done that, one then needs to redistribute the resulting compost.
An alternative could be to grow crops on a conveyor belt or set of panels which could carry and dump the mature plants into an enormous, more efficient, digester. The system could possibly float on water which would minimise the cost of (very slow) transportation. A cycle would take many months.
Indeed, but this is about building a factory. The advantage of the electric cow is that it approximates the land usage and management properties of a real cow (i.e. would you rather build an energy factory in the nearby field, or put a few electric cows in there?).
If it were to be built at sea, the energy for transportation could be provided by tide or wave.
But why would you grow grass at sea? If you are using large areas of sea for this, you have other sources of energy that are already available, and the land management issues do not arise.
-
We're basically talking about the most efficient way of harvesting solar energy, here. There are a million and one ways of doing it but live mammals are amongst the least efficient. If we are using plants to do the basic energy capture then, as long as the plants all 'crop' at a similar time, the large harvesting machine (combine harvester style) would seem to be the most efficient.
Despite being aesthetically attractive, I think the mechanical cow would need to be pretty large to be optimal.
-
I would disagree with your notion of efficiency on two counts.
My main concern is your insistence that plants are harvested at one time.
Yes, this can provide efficiencies of scale in gathering the crop, but looking at the wider process, one has to ask two question.
The biggest problem is availability of energy. Energy demand exists throughout the year, but if the crops are all collected over a few days, that is about 360 remaining days of the year you need to support the energy demands of your population.
There are ways of spreading the energy output (either store the fuel, or store the energy), but this creates demands on land usage, and other costs, that must impact on your overall efficiency.
The other problem is the collection of sunlight. If you have (as an example) grasses growing up to 3ft, and harvest it back to 1.5ft, then you still have a remaining 1.5ft collecting sunlight. If you harvest the crop all the way back to the ground, then you have no remaining crop to collect sunlight until the new seedlings break the ground again.
How critical this is depends on the type of growing environment you have. If you have an environment which would be unable to support the crop for some part of the year, then cutting the crop back to the ground is no real cost; but if you are in an environment that can support some sort of crop growth year round, then cutting the crop back to the ground will have a cost in sunlight that is not being used for growth.
As I said, I can see lots of problems with the electric cow, but at present the same is true of many biofuels. One advantage with electric cows is not so much in energy terms, but in terms of wider environmental issues (i.e. of land usage and shared usage of land).
-
Cropping need not be done annually; it can be when the plant is the right size and would not have to cut to the ground. That might be just monthly. There is certainly an optimum length for energy collection when you are dealing with grasses; in a normal lawn, the ground still receives significant light, so that particular length may not be best. As long as growth is fairly uniform, you could do it that way.
I can see that 'intelligent gathering' might improve efficiency and your 'cows' could operate on rough ground - even mountainsides - but yields would be low and the project would be less attractive (mountains are best used for sheep; yum yum).
-
Yes, I agree, it is very much about, if it is valid at all, then applying it to specific environments, and not a generic solution.
As a business solution, I still rather doubt that it would be attractive, as I would expect that return on investment would be slight, so the question is one of technical possibility rather than whether it would work commercially.
But, then again, much of the criticism about biofuels in general is where they consume valuable prime agricultural land that might be put to better use growing food crops; so having a mechanism to make better use of marginal land for biofuels would be itself significant.
-
I don't know why it would be NECESSARY! Live Cows already do all this and provide us with meat for food. These machines would require design, manufacture, and periodic maintenance, and would eventually end up in a salvage yard, or landfill. A poor substitute for the lesser cost of livestock.
People in rural India raise livestock, and compost the waste for fertilizer and fuel to heat their homes, run their vehicles, and cook their food, which includes the animals that produced the fuel. That's Efficiency!
The lack of efficiency like this is what's polluting our world and ruining our economy. Every one of the more than 6,000,000,000 people on the globe is their own potential source for fuel. This is before you figure in all of the other plants and animals.
Instead of creating new ways to make fuel, which ultimately end up adding to our problems, we should focus on using that which is already here. It would be a step toward reducing the greenhouse gas build-up, which will continue to rise with the population.
-
But mammals, like humans, consume energy even when they are 'just standing, doing nothing'. That accounts for most of their energy throughput, which is very wasteful, even if their faeces and their carcasses are used in the end.
This fact is the reason why poor communities where the food availability is marginal have to live on plants and can't afford to raise meat cattle.
A well designed machine could pay for its manufacturing energy relatively quickly and, after that, it would all be profit.
Of course - not an ounce of charm!
-
But mammals, like humans, consume energy even when they are 'just standing, doing nothing'. That accounts for most of their energy throughput, which is very wasteful, even if their faeces and their carcasses are used in the end.
This fact is the reason why poor communities where the food availability is marginal have to live on plants and can't afford to raise meat cattle.
A well designed machine could pay for its manufacturing energy relatively quickly and, after that, it would all be profit.
To an extent this is true, but where's the profit in making more Methane, when for the most part, it is going unused and becoming an environmental hazard? I see more potential in finding ways to use what is already being produced.
(Just mended your inbedded codes to make the quote show)
-
I fully support you opinion that we should use as little energy as possible.
However, this thread was really about producing the energy we do use in as efficient way as possible.
-
My dad told me a story of an artificial 'cow':
when he worked at Queen Mary College, London in the late '70's someone turned up offering artificial milk! It was pale green & I believe he tried it, which tasted vaguely milk-like!
The device for making milk supposedly fitted with a hopper filled with grass connected to a bio-degester.
So, rather than making electricity -develop this technology & save power by simplifying milk production. It would also mean vegans like my brother could again drink 'normal' milk!!
-
I fully support you opinion that we should use as little energy as possible.
However, this thread was really about producing the energy we do use in as efficient way as possible.
This is why I mentioned rural India, where they produce it from the wastes already produced by daily living and food production.
We're saying the same thing, but your answer is smarter cows and mine is smarter humans.
-
The problem with cows (not so much in rural India, but under the 'yoke' of mass farming techniques) is they not only make milk & become beef, but give off methane (pooh!) which is at least as environmentally damaging as transport emissions.
-
The problem with cows (not so much in rural India, but under the 'yoke' of mass farming techniques) is they not only make milk & become beef, but give off methane (pooh!) which is at least as environmentally damaging as transport emissions.
You are right, the GWP of Methane(its Global Warming Potential relative to CO2) is 21.
The real problem is that cows, wetlands, rice paddies, municipal compost heaps, and other large-scale methane producers show no signs of disappearing in the near future. The logical solution would be to burn as much Methane as we can, leaving CO2, and dividing its effect on the environment by 21.
-
The problem with cows (not so much in rural India, but under the 'yoke' of mass farming techniques) is they not only make milk & become beef, but give off methane (pooh!) which is at least as environmentally damaging as transport emissions.
You are right, the GWP of Methane(its Global Warming Potential relative to CO2) is 21.
The real problem is that cows, wetlands, rice paddies, municipal compost heaps, and other large-scale methane producers show no signs of disappearing in the near future. The logical solution would be to burn as much as we can, leaving CO2, and dividing its effect on the environment by 21.
Indeed. Where practical, such as landfills, methane would be better collected & if, nothing else, burnt. This is only a tiny % of emissions though.
80% of agricultural greenhouse gases are livestock related.
As I'm sure will be possible soon, a lab/factory could be set up to 'grow' real meat artificially (by tricking cells into becoming meat).
And milk could be made using biological breeders.
If these hypothetical technologies were available to all, the potential environmental reward would be huge.
Of course, the biggest battle would probably be getting people to eat & drink the stuff!!
-
Why not fit cows with catalytic converters at both ends?
-
The problem with cows (not so much in rural India, but under the 'yoke' of mass farming techniques) is they not only make milk & become beef, but give off methane (pooh!) which is at least as environmentally damaging as transport emissions.
You are right, the GWP of Methane(its Global Warming Potential relative to CO2) is 21.
The real problem is that cows, wetlands, rice paddies, municipal compost heaps, and other large-scale methane producers show no signs of disappearing in the near future. The logical solution would be to burn as much as we can, leaving CO2, and dividing its effect on the environment by 21.
Indeed. Where practical, such as landfills, methane would be better collected & if, nothing else, burnt. This is only a tiny % of emissions though.
80% of agricultural greenhouse gases are livestock related.
A tiny percentage with 21 times the environmental kick as the same volume of CO2(nitrous oxide rates 310, cfc's in the thousands). Any reduction in these concentrations does as much toward reducing global warming as 21, 310, or many thousands of times as much CO2. Coupled with the current "fuel crisis", methane development is Win-Win.
-
Its not grass that does it, it's digested grass, or to use Karen's terminoloy 'cowpies'. And yes if you did use cowpies instead of grass, your scheme could easily work.
-
wow but remember input is not always equal to the output so after all this u will get energy just to light up ur bulb.