Thursday, August 6, 2009 7:25:14 AM
Scientists in Minnesota are reporting that production of bioethanol — often regarded as the clean-burning energy source of the future — may consume up to three times more water than previously thought. Their study appeared in ACS' journal Environmental Science & Technology
The growing demand for bioethanol, particularly corn-based ethanol, has sparked significant concerns among researchers about its impact on water availability. Previous estimates failed to account for widely varied regional irrigation practices, the scientists say. The scientists made a new estimate of bioethanol's impact on the water supply using detailed irrigation data from 41 states.
Prior studies have estimated that a liter of bioethanol requires 263−784 litre of water from corn farm to fuel pump, but these estimates have failed to account for the widely varied regional irrigation practices. This paper estimates the state-level field-to-pump water requirement of bioethanol across the nation. The results indicate that bioethanol’s water requirements can range from 5 to 2138 litre of water per litre of ethanol depending on regional irrigation practices.Reference
Chiu et al.Water Embodied in Bioethanol in the United States
Environ. Sci. Technol., 2009, 43 (8), pp 2688–2692
Sunday, July 26, 2009 5:51:28 PM
In a post
of 3 October 2007 I wrote about the world's first prototype osmotic power plant, which uses sea water and fresh water separated by a membrane to produce energy. The Norwegian company Statkraft is continuing with the project and now building the world’s first full-scale commercial facility for osmotic power generation
, expected to be ready by 2015.
A paper to be published online in Physical Review Letters
describes another (new) way of getting electricity out of water. Mixing salt water and fresh water in a container with carbon electrodes can produce clean, renewable energy, and the reaction’s main by-product, brackish water, can be dumped back into the sea.
In the first stage of the process, salt water is pumped into a container with two charged carbon electrodes. Salt ions — positively charged sodium and negatively charged chloride — are attracted to the surface of one of the two carbon electrodes, depending on the ions’ charge. Next, fresh water is pumped into the container, and the salt ions diffuse away from the surface of the electrodes and mix in the fresh water. Pulling the salt ions away from the charged electrodes creates increased energy in the system.
So far the method is not perfect, but it is a fact that we do have to look for new sources of energy, preferably renewable energy.
Wednesday, October 3, 2007 6:18:32 PM
Statkraft in Norway has decided to build the world's first prototype osmotic power plant. Osmotic power is a renewable energy source. Osmotic power is based on the natural process of osmosis
(where water of low salt concentration will flow through a membrane to dilute water of high salt concentration until equal concentration on both sides of the membrane is reached). In an osmotic power plant, sea water and fresh water are separated by a membrane. The sea water draws the fresh water through the membrane, thereby increasing the pressure on the sea water side. The increased pressure is used to produce power.
The global technical potential for osmotic power production is estimated at around 1600 TWh, including around 200 TWh in Europe and 12 TWh in Norway, or 10 percent of Norway’s current power production.
Statkraft press release of 3 October 2007 at http://www.statkraft.com/pro/press/Press_releases/2007/1157666.asp
how it works.