How do you go about creating a viable Methane generator for generating electricity? Well, the concept is fairly simple, but there are a number of implementations.

I began researching this topic recently, specifically looking at the use of seaweed for Methane generation. In the area I live, seaweed is abundant. It also is smelly and an unsightly mess when it's left to rot on the beaches. So why not take that decaying resource and use it to generate power? Well, it actually is a feasible concept, but the ROI just doesn't make it feasible. Here's the analysis:

To develop a simple Methane digester (or Anaerobic Digester), I looked at a model that appears to making money: the farming industry. Dairy farmers today are taking manure and using it to fuel anaerobic digesters on a scale that allows them to produce between 4.0-5.5 kWh of energy per cow every day. That adds up when you look at farms that have between 500 and 1000 heads of cattle! Below is a diagram of how this system might be set up:

In a simplified view, there's really two main components:

• The anaerobic digester tank
• The generator

So how can this be applied to the seaweed digester? Well, there are a few things to consider.  Japan did a study in late 2006 on just how much energy you could produce with such a system. There conclusions were that approx. 2200 lbs of seaweed yields about 777 ft³ of methane. Methane generates about 1,000 BTU per ft³. If you look at one the best microturbine generators on the market today, it uses about 394,000 BTU/hr to generate 30 kWh of electricity. That means we can generate for about 2 hours on our 2200 lbs. of seaweed, or make about 60 kWh of energy per day. Not bad, but here's where reality kicks in. 2200 lbs. of seaweed costs about $66 at current market prices, but we only generate (at $0.12 per kWh) about $7.20 worth of electricity. That's where the economics of it breaks down.

So what's the conclusion of all of this? Well, in order to make Methane generation with seaweed feasible, you need to generate enough electricity to offset the cost of the raw material, plus make a profit. The break-even point for 2200 lbs. of seaweed is therefore 550 kWh of power generated, which translates to 7,223,333 BTU of energy. In raw Methane means 7,223 ft³. So the production needs to be increased by an order of magnitude in order to even consider it.

Of course, the alternative is to find another source of raw material that either costs less and/or produces more Methane.

Last update: 09-02-2008 22:24