Well one idea in Taiwan is to make briquettes from rice straw, burn it and then return the ash to the soil, since they burn it anyway in the fields. Maybe farmers could use this in wood burning type stoves to heat their homes in Winter.
Personally, I think this is solving a problem that doesn't exist. If people designed and built their houses properly here, they would need very little in the way of climate control. Yet they insist on building them to a temperate-climate design, out of unsuitable materials, and then when they find the building has pisspoor thermal performance, they throw energy at the problem with heating systems and A/C. Whether that energy comes from the grid or biofuels is immaterial - it's still energy that could have been used for something more productive, or not used at all. And again, if you must have climate control, the most efficient solution is solar-heated hot water.
As for the rice straw: they burn it because rice straw carries disease, but that wouldn't be a problem if they practiced proper crop rotation and/or polyculture. They could then leave the straw on the fields, where it belongs. Technically it would work, though. Rough guess: 1tonne/ha. dry weight containing 20MJ/kg = 20,000MJ = 5600kWh/ha. If you consume 20kWh/day in your boiler for 3 months (1800kWh) then you'd need about ~0.3ha. to heat your home. 0.3ha. would be considered a large field here, but not outrageously so.
Ideally, I suggest biofuels should be shaved from some perennial crop; otherwise, you've left a big patch of bare dirt that's going to erode very fast.
I once heard that high rise living was the most eco-friendly way of living in terms of energy/water use. Seem plausible to me.
I completely disagree, from a systems design point of view. We had a good discussion about that elsewhere.
I also want to add water consumption and reduction to this thread. I'm constantly horrified how much water is wasted. We really could put waste water to much better uses.
Yeah, that's true, but people tend to think in terms of domestic waste, which is a drop in the ocean (haha) compared to what gets used by agriculture and industry. It's quite a subtle issue. Waste is only truly "waste" if the water is polluted in some way, for example by detergents or agricultural chemicals. There's nothing wrong with taking a 200-litre shower and dumping the water back into the river. It just re-enters the water cycle and all is well. The problem is that you've also dumped 200x4.2x25'C = 21MJ = 6kWh of energy down the drain too (assuming it was a hot shower), and the detergents you've used will have some adverse affect on the river ecosystem, especially if you're one of a million other people doing the same thing. What unregulated industry does is a hundred times worse. Fertilizer and pesticide runoff also causes major ecosystem disruption.
One particular "waste" of water that irritates me is the management of urban runoff. A lot of city infrastructure is devoted to catching, channelling and "disposing of" rainwater. A properly-designed city should (a) contain mostly green spaces that will naturally use this water to produce something useful (biofuel, food, whatever), with minimal costs or human management; and (b) collect, store, and locally filter water from rooftops for domestic use. To collect water in reservoirs and then build a cats-cradle of pipes to distribute it (and a parallel network to throw away water that falls out of the sky!) is utterly ridiculous. I have no idea who came up with such a stupid design, but we ought to have an annual celebration like Guy Fawkes' where he's drowned in effigy.
Anyway, like you said, these things are all interrelated. You can't just talk about CO2, or energy, or water use, or environmental pollution; they're inseparable. That's what makes this stuff such an interesting topic!