Tag Archives: gas emission

Straw as Building Material for Future

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A modern take on straw-bale construction may well be the grand design of the future if results coming out of the University of Bath are accepted by the construction industry. Think of a straw-bale house and you might imagine a tumbledown shack that leaks, creaks, slumps and smells somewhat of the farmyard. But step into Bale-Haus, a startlingly contemporary looking prototype home that has been built on the Bath Campus and there’s nary a wisp of straw to be seen. Instead, you are in a hallway of an upside down house with two bedrooms and a bathroom on the ground floor and an airy open plan living area upstairs. It feels like a little piece of Scandinavia has just arrived in Somerset, southwest England. The straw bales are all packed tightly inside a series of prefabricated rectangular wooden wall frames, which are then lime rendered, dried and finally slotted together like giant Lego pieces called ModCell panels.

People perceive straw houses as being a bit hippy and not particularly durable. Add to that the problems of getting mortgage – very few lenders will consider straw-bale construction. The benefits of straw, points out Professor Peter Walker, director of the University of Bath’s BRE Centre for Innovative Construction Materials, are that “it’s cheap, widely available and a good insulator. It’s been used in buildings houses for hundreds of years”.

The stack that remains after grain has been harvested – straw also helpfully soaks up carbon from the atmosphere and locks it in, so long as it is not allowed to decompose. For the building industry, which currently depends on materials with very high embedded energy costs -  concrete and brick are expensive in carbon terms both to make and to transport – straw could therefore offer a welcome solution to housing’s greenhouse gas emission.

The straw-bale house won’t get sopping wet in a thunderstorm or go up in a whoosh of flames if you knock over a candle. The results now being published by Walker and his research partner, Dr Katharine Beadle, who have spent the past 18 months testing the BaleHaus against an exhaustive list of risk factors that could rot it, burn it or blow it down, so far seem to be reassuring.

Beadle with his team took a ModCell unit to a test laboratory and tried to reduce it to ashes by strapping it to a fiery furnace and raising the temperature to over 1,000 degree Celsius. “It’s standard test to replicate a fire in a building.” explains Walker. “It means you know that a house will at least retain its structural integrity for half an hour, which gives people a chance to get out”. “It took an hour and a half of being in direct contact with the flames”, says Beadle, before the lime render began to drop off, “and then the straw did start to burn back, but because it’s so compacted it suffered more charring then actual disintegration.”

When it come to blowing the house down – hydraulic jacks were placed against the walls to replicate wind forces pushing against the bales – the ModCell panels moved a few millimeters, but stayed within the tolerances allowed for by the computer modeling carried out prior to its construction. That says Walker, could be very good news for the price of the eventual ModCell building system. “It means the house is stiffer than it needs to be.” The approximate cost of the current modular building system for this design is £132,000 from above the concrete slab. “Cost is a challenge to the introduction of this technology but as a prototype house I think it stacks up well,” said Walker. “The aspiration is that it should be cost competitive with more savings coming through reduced heating bills.”

To replicate the heat given off by humans and appliances arrays of incandescent light bulbs on timers blaze in every room at pre-programmed times of day “to see how much heat escapes, and what level of heating would be needed at different times of the year,” explains Beadle.

“That environmental modeling will give us all the numbers about the energy the house is predicted to use. And if we are predicting how it will operate in given climate change, we can then put in those variables.”

Sensors embedded within each wall panel constantly monitor the degree of moisture absorbed and then released back through the breathable lime render into the sir outside by the panels. And on the air tightness test that was carried out, BaleHaus came in way under the building regulations threshold, and did considerably better than the far lowest “best practice” standard.

- The Guardian

Conventional farming limits greenhouse gas emissions

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Advances in conventional agriculture have dramatically slowed the flow of greenhouse gases into the atmosphere, in part by allowing farmers to grow more food to meet world demand without ploughing up vast tracts of land, a study by three Stanford University researches has found.

The study which has been embraced by many agricultural groups but criticized by some environmentalists, found that improvements in technology, plant varieties and other advances enabled farmers to grow more without a big increase in greenhouse gas releases. Much of the credit goes to eliminating the need to plough more land to plant additional crops.

The study’s authors said they aren’t claiming modern, high production agriculture is without problems, including the potential for soil degradation through intense cultivation and fertilizer runoff that can contaminate fresh water.

But some environmentalists said the study is flawed, arguing it’s based on unrealistic scenarios of what would have happened if yields hadn’t increased during the study period. The yield is the amount of a crop grown per acre.    agriculture

The other authors are Jennifer Burney, a physicist who focuses on energy and food security research at Stanford’s Program on Food Security and the Environment, and David Lobell, an assistant professor of environmental science at Stanford who has studied the effects of food and bio-fuel production on the environment.

The three decided to look at the impact of agriculture on greenhouse gases – carbon dioxide, methane and nitrous oxide. Agriculture accounts for about 12 per cent of greenhouse gas emissions generated by human activity.

The researchers set up hypothetical models in which the world’s growing population was fed by cultivating even more land. Those models were then compared with actual agricultural production between 1961 and 2005.

Yields for major crops like corn and soybeans have increased dramatically over the study period. Midwestern corn farmers for instance now average well over 160 bushels an acre. That’s roughly double what they produced in the early 1960s, according to US Department of Agriculture statistics.

Without those increases, it would have taken an additional 4.35 billion acres to feed the world according to the study. The cultivation of that land including the release of carbon in the soil and burning of brush and trees that covered it would have released an additional 317 billion to 590 billion tons of greenhouse gases, the authors wrote.

Stopping CO2 emissions cannot avert climate change

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With carbon dioxide (CO2) in the air approaching alarming levels, even halting emissions altogether may not be enough to avert catastrophic climate change. A new study by Carnegie institution scientists suggests that while removing excess CO2 would cool the planet, carbon cycle complexities would limit the effectiveness of a one time effort. To keep CO2 at low levels would require a long term commitment spanning decades or even centuries. Previous studies have shown that reducing CO2 emissions to zero would not lead to appreciable cooling because CO2 already within the atmosphere would continue to trap heat.                       emission

For cooling greenhouse gas concentrations need to be reduced. “We want to see what the response will be if carbon dioxide were actively removed from the atmosphere,” says study co-author Ken Caldeira of Carnegie’s Department of Global Ecology. Caldeira and study co-author Long Cao did not focus on any specific method of capturing and storing CO2 from the air. The posibilities include approaches as diverse as industrial scale chemical technologies and changing land use so more CO2 is naturally absorbed by vegetation.

According to the simulations conducted by the researchers, for every 100 billion tonnes of carbon removed from the atmosphere, average global temperature would drop 0.16 degree Celcius, said a Carnegie institution release. Further simulations showed that in order to keep CO2 at low levels, the process of CO2 extraction from the air would have to continue for many decades, and perhaps centuries, after emissions were halted.