From: Issue 29
I refrained from holding my nose and took a sip of lukewarm water from a plastic cup. ï»¿“good, uh?” said Jose Alonso Cozar, manager of the water desalination plant, with a genuine smile. I nodded, still not sure if I exactly liked it per se, but I was thirsty and the postocean cocktail was at least drinkable.
Despite being surrounded by water, the Spanish region of Andalucia is thirsty. To investigate this problem and take a sip of the proposed solution, I had come to spend the day at the Planta de la Desaladora de Carboneras, in the city of Carboneras on the southern Mediterranean coast of Spain.
It struck me as slightly odd that I was in southern Spain tasting water, not wine like most foreign visitors. The irony of the day continued when upstairs in the executive offices, I noticed a dispenser of purified water in the air-conditioned hallway. When I pointed this out, Cozar chuckled and said, “We don’t actually drink the desalinated water ourselves—we buy bottled water.”
On a quest to determine whether desalination is indeed a good answer to the global water shortage (it is estimated that one third of the world’s population lives in countries with significant water stress), I visited Carboneras to see Europe’s largest desalination plant. Funded by a grant from the European Union for economically disadvantaged regions, the plant cost 254 million euros to build and was intended to supply potable water to the arid south. The plant is publicly owned and privately operated.
Capable of providing 500,000 people with 120,000 cubic meters of desalinated water per day, the plant runs at only 15 per cent of its capacity. According to the general manager of another nearby desalination plant in the city of Almeria, the problem is that “citizens don’t want to pay more for drinking water when they know the city can just pump it from the ground…plus they simply don’t like the concept of drinking desalinated ocean water.” However, the local aquifer has only a few decades of water left, if consumed at current rates.
With greenhouses full of tomatoes sprawling for tens of kilometers in every direction of the Carboneras plant, I wondered why they don’t sell desalinated water for agricultural use. As it turns out, tomatoes don’t need potable water, and farmers wouldn’t pay for it anyways.
The plant desalinates ocean water through the process of ‘reverse osmosis’ where pressure is applied to the water, forcing it through a semi-permeable membrane allowing water, not salt, to pass through.
“To try to keep our costs down, we desalinate water at night when electricity costs less,” says Cozar. “From 8:00 am to midnight the plant is mostly quiet.” The process is energy intensive, using 4.7 kilowatt hours (kWh) per cubic metre of water produced thanks to the multiple pumps and‘turbopumps’ bringing water from the sea through a series of holding tanks, and finally back to the ocean as salt-concentrated wastewater. (In comparison, the average car uses an equivalent of 0.96 kWh to drive a kilometre, and a cubic metre is roughly the size of the box a new washing machine might come in.)
All of the electricity used in the desalination process is purchased from the Spanish grid. A large portion of this energy is provided by carbon-intensive sources, with gas and coal making up 55 per cent in 2007, as well as non-carbon intensive sources like nuclear (18 per cent) and hydro (up to 30 per cent). According to Professor Ricardo Barcelona from Spain’s IESE School of Business, “Despite the abundance of windmills you see in southern Spain, wind energy contributes, depending on the day, a maximum of only ten per cent of the installed capacity of the national electricity grid.” With desertification problems worsening every year in southern Spain, along with the increasing demand to grow crops in the hot, sunny climate, there is irony in the fact that the more water that is desalinated, the more greenhouse gases are emitted, and in turn, the faster the desertification.
Desalination was starting to look a lot less like a clean technology.