- Fast-forward the development of recycling and composting. It wasn't until the mid-2000s that compost or yard waste bins were common, and while recycling boxes were known by the 80s, their use didn't grow huge until long after that. Reducing the amount of stuff people throw out can be moved forward very easily, just have people pay more attention to what they already know earlier.
- North America keeps on moving up the CAFE requirements, and does not exempt light trucks and SUVs from them. As these vehicles were profitable they would still be made and sold (though probably in smaller numbers than OTL) and they would be more efficient, with lighter-weight bodies, more powerful V6 engines instead of V8s and inline-4s in the place of V6s on smaller models, the minivan stays more common and so does the family station wagon. Crossover-type vehicles come around a decade or so before they did OTL. This would also rub off on other parts of the world where such vehicles are common, such as Australia and the Middle East.
- Make cars lighter by developing aluminum unibodies (first used by Audi in the 1995 A8, but possible long before then), FRP bodywork (known and used widely in sports and racing cars since the 1950s) and expanding the use of carbon fiber in many vehicle applications that don't cost huge sums, such as axles, input and driveshafts, subframes, et cetera. As carbon fiber gets easier to make and cheaper, begin making more of the car out of it.
- Connected to the above, mandate higher-quality gasoline and ultra-low-sulfur diesel fuel be made more in refineries. Higher-quality fuel beign widely available means automakers can design cars for it, further improving their efficiency, and most such fuel also produces lower carbon monoxide and hydrocarbon emissions.
- Development of electric cars can't be fast-forwarded that much, though having somebody like Elon Musk (founder of Tesla) come forward with a car company dedicated to electric vehicles in the mid-1990s would probably assist this. Having GM have faith in the EV1 program and allowing the cars to be sold to their owners in numbers in the late 1990s and early 2000s and then having them start making hybrids at the same time would be helpful. The engineering of electric cars is not hard, but there needs to be a way of rapidly recharging them for them to be completely viable as a gasoline replacement. Tesla's Supercharger system is the best system for this so far, but really they need to get the charging time down to ten minutes or less for a full charge for this to full work.
- Alternative fuels make sense if done properly. Biodiesel and ethanol fuel are usable, but only if produced in quantities that do not require huge energy inputs - but bioreactor-produced algae based biodiesel and cellulosic ethanol can fit both bills. If these are produced more, then you can reduce gasoline consumption this way. Ethanol requires more fuel but burns hotter than gasoline does, and while it does produce more nitrogen oxide emissions, it produces far less carbon emissions. Making ethanol from corn as done now is energy-wise moronic and has the side effect of raising food prices, which is obviously undesirable.
- Have wide-scale electrification be common on freight railroads, and expand high-speed rail in North America. The Midwest is one of the most fertile markets in the world for HSR if the governments involved had the guts to really drop the money on building an HSR system. HSR would take passengers from short-haul air travel (frequently one of the worst emitters of all in transportation) and could reduce emissions markedly if the electricity involved was not produced through the burning of coal which is common in North America, Australia, South Africa and parts of Western Europe.
- TxCoatl is right about the need to advance nuclear energy, which means both competently building and operating the facilities in appropriate places, maintaining public confidence (this is a MAJOR problem in North America, Oceania and parts of Asia, where a sizable chunk of the local populations are avowedly anti-nuclear for this reason) and effectively dealing with the high-level and medium-level waste left behind. What helps the reprocessing case is the fact that reactor waste is mostly composed of uranium-238, and that the dangerous products from a reactor can be isolated in much smaller amounts. (And better still, one of the most troublesome isotopes in high-level waste, Technetium-99, can be transmutated using neutron bombardment into Ruthenium, which has a number of industrial uses.) Developing reactors which can burn up the actinides from the original reactor would improve this further.
- Develop graphene and aerogel into wide-scale commercial uses. Seriously, this one would be enormous. Graphene is an excellent electrical conductor and its wide availability will enormously reduce the difficulty of desalinisation and production of alcohol, both for fuel and human consumption purposes, as well as potentially replacing silicon in semiconductors and using it in electrical components, including piezoelectric systems and solar cells. Aerogel, in addition to it not weighing anything, would be revolutionary in materials science for its insulation properties, as well as for catalysts, superconductors and water purification.
- Deforestation could be contained through the use of other materials for construction purposes. One of the largest uses for logging in modern times in North America is for house construction. One could replace these with steel (or for maximum green effect, recycled steel) or other building materials if one is dedicated enough. One good way of getting this would be to start in the earthquake-prone American West Coast by mandating that buildings be built to withstand earthquakes to a degree impossible with wooden-frame houses, thus forcing the development of metal-framed houses.
- As foolish as it might sound at first, one of the ways to go for reducing waste would be incineration and other ways of energy from waste technology, in this case an incinerator that does not vent its pollution to the environment but rather captures everything into a facility that could turn it into other products, as there are few byproducts from a waste to energy facility that cannot be reused in some form.
