A very tough one to appraise as the end user could be a watch dog group (ala Ralph Nadar), the automobile industry, or any other industry.
This is a very very hot topic and in the news daily on NPR, the internet, and many major newspaper and television features.
Going into election year here in the US this is even going to be bigger as candidate are trying to sway the "green teem".
Global warming, fossil fuels, and industry...just heard on the news this am that China is the number one consumer of coal in the world using more than the US, Russia, and Japan combined. Plus, in order to meet their growing needs and power consumption, China is building 500 coal fired power plants by the year 2010 with many nearing completion now.
So, this will indeed stay in the news for quite sometime.
Emissions does not solely apply to auto emissions but also to power plant and industrial emissions.
You are quite possibly sitting on some very trendy and hot keywords and keywords that I think are going to get quite a bit of attention in the years to come.
I have no idea of the offers made. I would not let this go cheap.
What I would do, if it was mine, is get someone to build a site regarding pollution, global warming science, and emissions with RSS feeds and Google adsense. As a site, this will make it even more of an appealing buy.
If it cost you 100 bucks, so be it. You could potentially be looking at $5K-$10k and potentially much more depending on the enduser and what their use for this will be...political, anti-industrial, EPA watchdog group...
You have a good one; just one that is difficult to put a price on.