concrete and other problems

We have included a couple of interesting facts about concrete to help illustrate the point that in environmentalism things aren't always quite as straightforward as they might be portrayed to be. Plus, it might make you think twice about ripping up and re-concreting your driveway just because it is looking a bit shabby.

Concrete was first used by humans around 6,500 years ago. Modern production of cement creates a lot of carbon dioxide, up to 1 ton of CO2 for every 1 ton of cement produced. Cement production accounts for approximately 7% of world-wide greenhouse gas emissions.

Hydroelectric power generation is thought of as green energy. However, hydro schemes require dams, which are made of concrete. The Clyde Dam contains 1,000,000 tons of concrete. If you calculate the embodied energy of the cement required to build the dam, it comes to around 6 hundred million megajoules. The power output of the Clyde power station is 7.5 million megajoules per year. So it will take 79 years for this power station to cancel out the embodied energy required to make it. The Clyde started producing power in 1993, so it should have that debt paid off by 2072. If it is still running by then, it will truly be producing green energy.

There are ways to make concrete more environmentally friendly. One way is to add fly ash. The addition of fly ash can reduce the CO2 producing ingredients of cement by up to 90%. Ironically, the main source of fly ash is coal fired power stations.


PAPER, CORNSTARCH, JUTE AND COTTON Bags - some inconvenient truths

Paper bags are often touted as being greener than plastic bags. Paper, it turns out, is a dirty business. We recommend that you do your own research. Here are a few categories you could select in order to make up your own mind. Just Google paper production and:

deforestation, air pollution, water pollution, water consumption, landfill methane, carbon monoxide, ammonia, nitrogen oxide, mercury, nitrates, benzene, volatile organic compounds, bleaching.

Much of the paper associated with food wrapping becomes contaminated to the point where you would not put it in your recycle bin. But even uncontaminated paper cannot be infinitely recycled (a maximum of 4 times until the fibres become too short to bind to each other). So what happens to all the paper that is not suitable for recycling. Unless you can burn it, it will end up in a landfill where it will, as we all know, produce methane.

And any paper with printing on it, has additional problems. Google: recycled paper and de-inking.

There are four main problems associated with the use of cornstarch bags. Firstly, their production takes valuable farm land away from food cultivation. Secondly, they don't break down as quickly as promised. This can be especially troublesome when they are labelled “Flushable”. Thirdly they contaminate plastic recycling. Being visually indistinguishable from petroleum based plastics, they are unable to be sorted from the waste stream. This a serious problem for those involved in recycling standard soft plastics. But the fourth and major problem they have is that if they end up in a landfill, which the vast majority of them will, they create methane. Plus any organic matter they contain will then be exposed to water and will also turn into methane.

Jute is hailed by many environmentalists as a saviour of the planet. More than 95 percent of the World's jute production occurs on the Ganges Delta, which sprawls across India's West Bengal and a large part of Bangladesh. If you know anything about Bangladesh, you will be aware that it is blessed with inordinate quantities of water (often way too much of it). Everything we grow has a water requirement. Potatoes, for example, have a water requirement of 287 M3/ton (cubic metres per metric ton). While not as thirsty as cotton, jute requires a large amount of water for its production (2,605 M3/ton). That is slightly more than the quantity of water in an olympic size swimming pool.  Approximately ten percent of this figure is grey water component, or water that is required to process to final product and is contaminated in this manufacturing process. With water becoming a scarce commodity in many parts of the world, it does not seem that there are many places where an up-scaling of jute production would be feasible. In case you are wondering, HDPE bags do not use any appreciable water in their manufacture. If a jute bag weighs 100gm then it took approximately 260 litres of water to produce the material it is made from (this does not take into account any further processing or dying that may have occurred).

And if you want to dispose of your worn out jute bag responsibly, please do not put it in your household rubbish. The safest thing you could do is burn it. That way, hopefully, all you will be releasing into the atmosphere is CO2 (provided it has no inorganic printing on it).

A comprehensive study commissioned in 2006 by the UK Government determined that a cotton bag would need to be reused a staggering 327 times to equal the environmental impact of using "single use" HDPE bags.

Everything we do has a cost.