For the most part, the technology used by the Eco-villains is polluting in nature or, at best, neutral. Generally speaking, Doctor Blight, Looten Plunder, and Duke Nukem are the villains that emphasis this tendency the most.
Doctor Blight usually uses her computer MAL. She also uses various vehicles in episodes for example the Blightmobile in The Littlest Planeteer and Turbo Blight in most episodes.
Duke Nukem supposedly depicts the dangers of nuclear technology. His episodes mainly revolve around the problems of radioactive waste materials, nuclear accidents, or energy usage in general.
Looten Plunder generally utilizes conventional technology to further his business operations. Occasionally, he purchases futuristic-yet-polluting technology from Dr. Blight or works directly with her to achieve his goals.
Normally however, while his schemes impact the environment, the pollution is just a side incidental, not a deliberate act.
The Slaughters specialize in poaching, and therefore use present-day technology to go about their business. They are seen using gas-powered vehicles and modern-day firearms.
Sludge's front-end loaders are automatic and controlled via a computer system. This can be seen in the episode Volcano's Wrath, where Wheeler and Linka are trying to figure out what his shrinking ray does. Wheeler overtakes Linka at the controls, pressing random buttons and prompting doors to slide open, revealing many front-end loaders. They then begin to drive about the room. One is even able to deposit a load (in this case, the character Lanai), on the platform usually reserved for piles of trash.
It should be noted, however, that Sludge still employs people to drive his machinery. Lanai can be seen driving a truck in this episode, though she later mentions needing to reconfigure the settings for the front-end loaders or earth-movers in order to drive them in a conventional way.
In the episode Volcano's Wrath, Sludge has built a garbage management facility on Laipuno Island. He claims to be shrinking piles of garbage using a shrinking ray. This is the first appearance of Sludge's shrinking ray - it also makes an appearance in the episode No Small Problem.
The first appearance of the ray is purely to fool people. The ray does not work - it creates a bright light that forces people to shield their eyes while Sludge disposes of the garbage via a trap door. It then travels along a conveyor belt and is picked up by large buckets that travel on a loop not dissimilar to a ski-lift. The garbage is dumped into a volcano.
In the episode No Small Problem, Sludge's shrinking ray does work, albeit temporarily. He manages to shrink the garbage and deposit it elsewhere before people realise he has not come up with a permanent solution. The Planeteers run afoul of Sludge's shrinking ray in this episode and are forced to scramble through a landfill and battle giant insects and trash before they can defeat him.