What happened Shares of renewable fuels and biochemicals company Aemetis (NASDAQ: AMTX) rose a swift 13% or so within the first hour of trading today. The sizable gain held strong, with the stock still up by about the same amount at roughly 3 p.m. EDT. The bullish attitude appears to be related to cows. So what Believe it or not, that last statement is couched in reality. According to Aemetis, it has received certification from the California Air Resources Board "for a new LCFS Tier 2 fuel pathway for the Aemetis Advanced Fuels Keyes ethanol production plant utilizing renewable dairy biogas as a process energy input." This approval is expected to help reduce the carbon intensity of the ethanol the company produces, so it is a positive development in and of itself for the environmentally focused company. Image source: Getty Images. That said, the current approval is part of a much larger effort. The company hopes to create a portfolio of 30 "dairy lagoon anerobic digesters" connected with up to 36 miles of pipelines that it will own. The goal is to expand this operation over time to include 52 dairies. You can use your imagination as to what gets placed into said lagoons, but suffice it to say that Aemetis made sure to highlight that "an estimated 25% of methane emissions in California is produced by dairy waste lagoons." This is one way of turning waste into treasure, to paraphrase an old saying. Now what Bad jokes aside, this is an interesting development effort, and the approval is probably an important win for the company. It isn't surprising that investors were pleased with the news. But with its roughly $680 million market cap, Aemetis is a fairly small company, and its clean-energy focus has garnered material attention from Wall Street of late. Indeed, the stock is up more than 900% this year alone. Long-term investors should probably tread with caution as it looks like a lot of good news has been priced in here in a very short period of time. 10 stocks we like better than AemetisWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Aemetis wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of February 24, 2021 Reuben Gregg Brewer has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source