Mass balance analysis of algal biodiesel

Physorg.com reports on a recent paper in which the authors analyze the sustainability of algal biodiesel from a mass balance perspective. The paper, Bioresource Tech. 102, 1185, essentially highlights one of the tradeoffs with algal biodiesel. The low tech route of large containment ponds limits the total output of dry biomass per hectare, as evidenced by the author’s computation that even 11 square miles of algae ponds, at a growth rate of 50 g of bone-dry biomass per square meter per day, would only be sufficient to replace 0.1% of the US consumption of diesel.

Of course, there are many ways to increase the output per hectare. One of these are vertical tubes, or bioreactors, for algae growth. The issue with this approach is that it is capital intensive, requiring not only the tubes, but cooling systems to prevent algae death from overheating and requires higher overhead, since the tubes must be scrubbed occasionally to reduce fouling.

If I were to be looking at this area for technology breakthroughs, I’d be looking at people applying anti-fouling or other surface chemistry applications to reduce the maintenance costs, or clever engineers designing passive cooling systems for these reactors. I can imagine a system where the bioreactors were built to exchange heat with an HVAC system in cooler environments, or with their own ground-sourced heat pump in warmer times. The cost of the cooling is a major barrier and it would be a win to spread that cost around amongst several different systems.

Limitless solar?

One of the things I have been almost continuously talking about in the realm of renewable energy is the need to diversify our sources of energy. Another is the need to beware of people who preach that there is One True Solution. It was thus with great interest that I read about an upcoming paper in the Proceedings of the IEEE.

In this paper, Derek Abbott of the University of Adelaide argues that solar, and in particular, solar thermal, is the Ultimate Answer to the world’s energy problems.  In fact, according to Physorg, he claims that solar thermal can last us for “the next billion years.”

Despite this claim, the quoted numbers in the article and the conclusions are actually pretty reasonable in general. Solar thermal is the most cost-efficient (although certainly not the most space efficient) renewable technology in terms of energy yield.  However, stating that solar thermal by itself is sufficient for the next “billion” years is rather unreasonable.

Either Abbott presumes that the rate of growth of energy usage on the planet will slow down to nearly nothing or that we will eventually fill near-Earth space with solar collectors and ship either hydrogen or microwaves back down to Earth. No other possibility can justify his statement. As I calculated some time back, at modest growth rates, there is a much-closer horizon of about 500 years before we start running up against the limits of solar power.

There are also other issues in the article that should be addressed. The first is the cost, both capital and variable, of transmission lines in his scenario. If, as he suggests, we convert 8% of the desert land in the world to energy production, we are faced with the challenge of either building transmission lines to the hinterlands, which are on average about 30% efficient, or according to his scenario, generating hydrogen, liquefying it, and shipping it. I don’t know the efficiencies of electrolysis of water, or of hydrogen liquefaction, but in any case, there are three lossy steps here, before that hydrogen is either burned or passed through a fuel cell to make electricity.

Don’t get me wrong: in large part I agree with Dr. Abbott. Both my numbers and his point to the same conclusion – that solar must be a part of any renewable future. My primary concern about this article and others like it is that they will serve to skew the funding and research environment in renewable energy the same way that the biofuel craze has. We have a good way to go before we can replace fossil fuels in their entirety and it seems clear to me that as we transition away from a fossil fuel energy monoculture, we would do well to avoid another one.

Renewable Energy 101

This Friday, I’m going to be speaking at Asheville Green Drinks about renewable energy. The event starts at 6 pm and I’ll start talking at around 6:30. The blurb about my talk is up on the AGD website already, but I wanted to write a little bit about why I’m giving this presentation.

Talking to lots of people has made me realize that it is easy to be overwhelmed by the quantity of information out there about renewable energy.   Energy production and consumption is a complex topic and it is made more complex by those who have the most financial interest in the field tossing out truths and truthiness, often out of context, in order to solidify their position. And without some kind of base level of knowledge, its impossible to think critically about the news and propaganda that’s flying around in the media.

What I want to do is to give a quick overview of the state of the art in renewable energy – pros, cons, myths, and challenges. In addition, I’m going to talk about the size and scope of the “energy problem” that the world is facing and why its of utmost importance that we solve it, rather than deferring it or succumbing to it. I’m going to talk about why energy is the only true measure of wealth and how access to energy is a human rights issue. And, I’m going to end up by giving my perspective on what the ultimate solution will look like.

Its shaping up to be an exciting presentation.

World Crisis Index

Intrade, the Ireland-based prediction market, has launched a World Crisis Index. This index is a sum of the prices of 8 current markets Intrade is making in the area of global crisis, including a markets on recessions and growth rates in industrialized countries, US unemployment rates, the possibility of new US military action, and other issues. This sum is then normalized and reported. The Intrade markets first came to my attention via an email from Robin Hanson, who is arguably the world’s leading expert in prediction markets. Intrade had a good deal of success in predicting the outcomes of the last election cycle.

I followed the market fluctuations in the electoral issues pretty closely last year, specifically through Intrade’s partnership with Rasmussen Reports. What was interesting to me was how well the markets predicted changes in press coverage, from positive to negative or more interestingly, from sparse to dense and vice versa.

Geotagging and Google Maps

This is way cool: Google Maps API now supports a wide array of geotagged sites. In the example given in the link, a properly geotagged Wikipedia article will display a link on Google Maps at that site. Very nice! I expect to see a lot of organizations tagging projects or sites of interest in this fashion. Think about the Nature Conservancy tagging potential new acquisitions or a local chamber of commerce highlighting attractions in their town this way.