Tuesday, March 15, 2011

Humans and energy - the long view

In times of energy-anxiety it can be good to take the long view:

An extra stomach

Some hundred thousand years ago humans started to use fire. It was a first defining moment for humanity to use external energy for its purposes. Fire gave heat, but it also meant that we could eat things that we couldn’t eat before. Even for those things we could eat, the conversion of them to energy in our body was substantially improved. To heat food makes it softer and more easy to digest, even if the food doesn’t contain more calories through cooking, it uses less energy for digestion and more of the energy in the food can be absorbed. Some claim that cooking was a prerequisite for developing the human brain, which uses between 20 and 25% of all energy in food (the Economist 2009a). One could see it like fire is an external assistance to our metabolism. A cubic meter of firewood represents some 1 MWh, i.e. more or less a humans annual energy consumption in food. To make a serious camp fire to cook a deer you need some 50 litres of wood, i.e. 50 kWh. This corresponds to 15 people's daily energy consumption in the form of food.

Already the introduction of fire meant that we humans took substantial energy sources under our command. And still today, hundred thousand years later, firewood or charcoal (made from firewood) for cooking represents a very substantial parts of poor peoples’ energy use. As mentioned earlier, fire also played a very important part in the development of our tools, from its use to break rocks, to melting ores and burning pottery. In the emerging farming, fire was used for land clearing and for getting rid of waste and pests. Pastures were maintained and rejuvenated through regular burning. This is still a common, and necessary, practice. One might say that more than anything, possibly with the exception of the spoken language, fire was that made us human.

Oxen and mules

Introduction of drought animals some 6000 years ago was another form of conquering more power for human needs. Still today, there are some 400 million drought animals in the world and fifty percent of all agriculture land is managed with the help of drought animals. They are some 300 million cattle, including buffaloes, and 80 million horses, donkeys and mules (IFRTD 2009). The power of the animals varies from some 200 watt for a donkey up to 650 watt for a camel. They also endure in varying degrees, four hours for a donkey and up to ten hours for a horse (cattle certainly endure, but they simply spend so much time to eat and ruminate the food that they can’t work so long hours). This means that the daily energy output can be somewhere between 1 and 6 kWh (FAO 2000) to compare with the human’s 0.5-1 kWh. Drought animals thus meant a substantial extension of the power that could be put into our service. However, natural and biological conditions limit the use of them and their efficiency. In most agriculture situations they can only be used, or are only needed, in a rather short period of the year. Most importantly, they could expand the land brought into cultivation by increasing the land cultivated especially in the countries with very seasonal farming (the temperate climates or those with marked dry seasons). It is stated that a settler family with drought animals could farm more land than a whole Native American village could (Cunfer 2005). For trade, animals resulted in even bigger advantages; one human can easily lead five animals that all of them carry heavier loads than a human could.

Drought animals have to eat, so their use will be limited when land is scarce. They are easily kept in large numbers in areas where there is plenty of pasture that grows year round. In temperate climates, where the grass doesn’t grow in the winter, substantial areas of farm land had to be set aside for growing the feed for the animals. In slash and burn (swiddening) cultivation systems there is little space for drought animals, as the roots and the rubble in those fields make working with pulled tools difficult. In addition, the fire does a lot of the work in the first place, so the need for animal power is much less. In Africa south of Sahara, it was only in modern time drought animals were brought into use. A study from Mali and Senegal shows that drought animals represent 90 percent of the mechanical energy in the farms. They were introduced in Senegal, Guinea and Mali in the end of the 1920s, and the main effect was that the proportion of land that was cultivated increased from 30 percent to 40 percent in Senegal and from 40 percent to 70 percent in Mali (Faye and Faye 2009).

Wind and Water

Sail ships are shown on an Egyptian vase that is 5,500 years old. Wind is a good example of how it is not enough to know an energy sources to be able to use it. Anybody walking against a storm can feel the power, it is first when we know how to master and target it that it becomes useful. In its simplest form, wind energy was used, and is still used today for winnowing, separating the grain from the chaff by means of throwing up the grain in the air. The wind will then take the lighter chaff, twigs and other impurities with it. It took a long time before water and wind power became important for the production as such. Wind power was used mainly for milling and pumping and water wheels ran pumps, mills, and later in sawmills and trip hammers.

The most important use of these energy forms was for communication. The streaming water in rivers were used for transportation of various goods, but could of natural causes only be used one way. The real revolution was the introduction of sailing. Sailing allowed human expansion and increased trade tremendously; it also led to the distinct advantage for coastal areas for economic development, a pattern that holds still today.

Charcoal and wood

Wood has many uses. It has been the totally dominating fuel. It has been used for shipbuilding and housing and in all kinds of crafts and production from pottery to mining. Everywhere wood was needed and used. The energy intensity in wood can increase by making charcoal, that simplifies transport and storage and gives conditions for a more efficient combustion and higher temperatures[1], the latter was very important for the development of metallurgy. Most civilizations would simply have been impossible without forest and some of them collapsed because of collapsing forests. The deforestation of the Mediterranean is one such example. In Europe, the forest resources were approaching a collapse in the 19th century. Wood was used for more and more purposes and trade expanded rapidly. Similarly, as oil price hikes threaten to destabilize the world economy of today, scarcity of wood threatened the society 200 years ago. This changed when profitable uses of fossil fuel, in particular mineral coal, were introduced (Högselius 2008). Even a sparsely populated and forest rich country like Sweden had widespread deforestation in its mining areas in particular. In more densely populated areas with iron works such as in Luxembourg the wood price increased with a factor of 24 from 1611 to 1790 and in German Hunsrück wood prices increased almost hundred times in less than 150 years. This was also the background to the early forest conservation efforts in Germany.

Table 4: Wood price in Hunsrück 1655 to 1791











Source: Moreau de Gerbehaye 2002

A similar situation was apparent in Japan and China. Japan was largely deforested and the government took harsh measures to protect forests and to plant new forest. In some regions of Japan, saws were banned to protect the forest. One of the reason for Chinese decline can very well be a combination of soil erosion and deforestation (which often go hand in hand and feed each other). In 1949, Japan had restored forest so that they covered 68 percent of the land, while China had 8 percent (Radkau 2008).

Coal, natural gas and oil

The use of fossil fuels has increased 800 times since 1750, and has increased 12 times during the 20th century (Hall and others 2003). Fossil fuels represent some 80 percent of all energy supply today. There is no principle difference between coal, natural gas and oil, even if the practical usage differs a bit. They are all three created by photosynthesis and geological processes. Of the total stocks of fossil fuels, coal is dominating with some 70 percent and coal represents today 26 percent of the global energy supply. Coal is mined and used in all continents. We have already discussed the importance of coal for the early industries. Up to the middle of 20th century, mineral coal was the completely dominating fossil fuel and also gas and to some extent a liquid fuel was produced out of coal.

Petroleum (Oil) has been known for thousands of years and was used as a fuel from the mid 1800s. The comparative advantage of oil over coal is that it is more energy dense (50 % more energy per weight units) and that it is liquid and therefore easily regulated and fed into an engine. Compared to biomass, oil has an energy content per kg that is four times higher (Helmfrid and Haden 2006). Its primary use is for the transport sector where the petroleum derived gas, kerosene and diesel runs all kinds of vehicles, planes and ships. Ninety-five percent of the transport energy is from oil and today oil represents 34 percent of the energy supply.

Natural gas is cleaner than coal and oil, at its combustion, carbon dioxide, steam and nitrous gases are the main effluents. For this reason, gas is the most rapidly increasing energy source and represents today some 20 percent of the use (IEA 2008). The usage is limited by that natural gas is bulky and it has to be compressed for transportation and most uses.

[1] The total energy content of wood doesn’t increase by coaling, on the contrary opposite some energy is lost in the coaling process.

This is an extract from my book Garden Earth . I wil soon post something about energy today

You find selected other extracts from Garden Earth here

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