No, for a three-year cycle you need biomass coverage of 4 times the yearly consumption rate. If you harvest X Kgs of Biomass (that took Y years to grow) containing Z Kgs of Carbon. X Kgs of this biomass will absorb Z/Y Carbon per year. Therefore in order for the remaining biomass to absorb the Carbon back in one year will require Y*X Kg of living biomass. This is the sustainable crop size but is quite different from the yearly crop size except in the case of a yearly growth/harvest cycle.
The post I pointed you to early states the experts estimate the greenhouse gas efficiency at approximately 93% (I assume this is for a sustaining crop size). It also gives you some figures on the size of crop hat is currently required for this process.
It has been my experience that we as a species are not very good at the long term planning required to insure the effective maintenance of a carbon cycle energy production system. The effects are just to disperse and long term for most people to concern themselves with. This means that 7% inefficiency will never be taken care of until it comes back to bite us.
I must be missing something.
The whole selling point to fuel cells is supposed to be that they are much more efficient when used in, for instance, cars than an internal combustion engine. If a car on fuel cells can get twice or three times the mileage of a regular car, then it’s releasing half to one-third the CO2, even if it’s using a hydrocarbon for the fuel cell.
Right? Or am I being somehow dense?
I think that too many people consider that alternatives to fossil fuels need to rely on one technology only. A sensible mix based on local conditions makes more sense. For example:
Coastal cities can use the ocean of heating and air conditioning. Water of the deep continental shelf can be a heat sink in the summer and a sorce of heat in the winter. This technology is pretty basic .In places which are not near the ocean, the earth can serve the same purpose, although its capacity is not as great.
Solar hot water heaters on rooftops can be both a source of space heat and hot water for domestic or industrial purposes. Very low tech and very cheap.
Geothermal. Anywhere there is volcanism like the Cascadia subduction zone.
Waves. Wave power can be harnassed by using devices which are basically two barges hinged together. As they flex, a piston between compresses air to drive a turbine.
Wind, more wind.
Tidal power. New technologies promise to be able to do it without all the environmental damage of places like the Bay of Fundy or St. Malo.
And of course, Photovoltaic, which everyone agrues is not cost effective. Perhaps, by conventional economic theory, but with a serious research effort and with rising fossil fuel generated electrictiy, it would eventually make sense for every rooftop to generate electricity. To me it is a nobrainer. It is just a question of time.
You forget that there are two things that are serious considerations here - first, the power of pumping water to and from deep from the continental shelf, and second there is both a high capital and maintenance cost involved, especially with something dealing with seawater.
But to your second point here - while the ground may not have much heat capacity, Seasonal Thermal Aquifer Storage has been explored and used by some institutions. This works on a cycle where cold water is pumped up in the Summer, used to chill a building, then sent through solar collectors, heated, and pumped back down into the aquifer - about a quarter mile away. Then in the Winter, the reverse happens. The warm water is pumped up, used either to heat the building or to supplement a heat pump, then chilled outside, and pumped back down into hole #1. It can work, but has a very low efficiency and serious maintenance problems sometimes.
Also, some local environmentalists will then get after you for “disturbing the environment” - damned if you try to save the Earth, damned if you don’t (this actually happened at KU, when we did an analysis of using this sort of system to Heat and Cool the Foley Building on the West Campus. The environmentalist groups on campus, that we thought would be cheering us for being “clean green energy”, instead howled in protest that heating and cooling the aquifer would somehow “disturb the balance of nature” - according to a laughably incorrect editorial.)
I’ll give you low-tech, but see some of the past posts by sailor about their cost effectiveness and maintenance problems.
Well…you really do need some special circumstances to make geothermal power of any magnitude cost-effective. This is why this has not spread much further in use.
Inventive devices, but they are very low power output per $ of capital cost.
Many issues here…best covered in some past threads.
Tidal power can work too, but the power produced per dollar is very low. And the absolute value of the power is very low as well.
Well…you make my point. It is not cost effective with current technology and by current measures, but may be soon.
The approach to always keep looking, and doing what we can, is great and admirable. I just hope we can get fusion going sometime soon…
One argument I have heard against logging (from a biology teacher I once had) is that if material were left to decompose in the forest it would break down and help build up the quality of the (often poor) soil.
Doesn’t biomass farming ultimately deplete the soil? The stuff that gets burned is composed of more than just carbon. Is a system of crop rotation needed to keep this more self-sustainable?
It is indeed something you have to be careful about when planning a biomass crop. You do have to let a certain amount of the biomass fall back to the soil. This amount varies by crop, but is included in the “typical” 7% loss of CO[sub]2[/sub] reduction given for most biomass crops. Thus, you still will get a large amount of usable biomass.
You can look at current farm crop management to see how they do it as well. Some farms have been successfully using the same fields nearly continuously for 100 years here in Kansas.
One point that often gets missed when talking about rooftop solar collectors is that they are very dangerous. Currently, falls are the second most common cause of accidental death, and the number of falls per year would go up exponentially if we had complex rooftop systems that had to be repaired, cleaned, etc. We’re talking about thousands, maybe tens of thousands, of deaths and serious injuries per year, if rooftop collectors were in widespread use (say, by 20% of homes).
In my opinion, there will never be a form of energy that the greens will be happy with. Concentrated power is dangerous no matter how you collect it, and almost all forms of energy collection affect the environment in some way. You can bet that if we come up with a clean geothermal energy source, the same people protesting nuclear power will find some reason to protest that, especially after some accident kills a few people or does some damage to the environment.
Currently, hydo dams and wind power farms are both under attack by some environmentalists, and those two technologies were proclaimed as part of the future by those same people 20 years ago, when they were fighting nuclear power.
Anthracite, has anyone done a study on the effect of solar collectors on the environment? If we replaced all of our power needs with photovoltaic, how much mining of things like Gallium, Selenium, would be required? Would covering that much of our surface with solar collectors measurably affect the Albedo? How about the local environment that would be displaced by huge collector farms?
My thesis is that many environmentalists are always in favor of the NEXT power source, the one we don’t have yet. But once it becomes viable, they’ll find problems with it. If we wind up with millions of electric cars on the street, there will be screams about the environmental problems from battery disposal, and a few high-profile accidents that require an environmental cleanup will cause a new hue-and-cry from the same people now trying to make it law that a certain percentage of us be driving electric cars in the near future.