Under the issue of Environment:
"Competitive free markets and property rights stimulate the technological innovations and behavioral changes required to protect our environment and ecosystems. Private landowners and conservation groups have a vested interest in maintaining natural resources. Governments are unaccountable for damage done to our environment and have a terrible track record when it comes to environmental protection. Protecting the environment requires a clear definition and enforcement of individual rights and responsibilities regarding resources like land, water, air, and wildlife. Where damages can be proven and quantified in a court of law, restitution to the injured parties must be required."
And under Government Finance and Spending:
"All persons are entitled to keep the fruits of their labor. We call for the repeal of the income tax, the abolishment of the Internal Revenue Service and all federal programs and services not required under the U.S. Constitution. We oppose any legal requirements forcing employers to serve as tax collectors. Government should not incur debt, which burdens future generations without their consent. We support the passage of a 'Balanced Budget Amendment' to the U.S. Constitution, provided that the budget is balanced exclusively by cutting expenditures, and not by raising taxes."
So, unless it is shown to be constitutionally mandated a carvon tax is not endorsed by their platform.
If I read correctly, it would not be endorsed under their Crime and Justice section either.
Interesting aside, the Libertarian Party doesn't seem to be aware that all (100%) of U.S. currency is based on debt. The Treasury issues a bond, the Fed lrints money to buy it, and then all that goes into circulation. It's not magic, it's explicitly fiat, but I guess they missed that, or want to go back to something like the gold standard, which totally makes sense if you believe in the intrinsic value of gold rather than simply inderstanding it as a convenient means to mark a currency against if you want to limit inflation as only so much gold production per year is possible.