Regular bell peppers fall under the category of general vegetable waste generated during food preparation that can be added to a compost worm bin. You can add whole spoiled peppers, ideally chopped up into smaller pieces, or the tops and membranes of wholesome peppers after slicing the walls. If you don't want pepper plants to potentially sprout in your compost bin, wash the seeds off the membranes and discard them elsewhere.
One exception to the rule of "if it comes from the ground, it can go into the worm bin" is the hot pepper. Hot peppers can burn your skin and mucous membranes, as is the goal when you add a habanero pepper to a sauce to provide a spicy, burning taste. The active ingredient is capsaicin, produced in the pepper membrane rather than in the seeds as is commonly thought, explains horticulture educator Jennifer Schultz Nelson of the University of Illinois Extension. The Scoville scale measures the hotness of peppers.
Hot peppers can indeed burn earthworms the way they burn human mucus membranes. Worms are sensitive to irritating chemicals, U.S. Forest Service ecologist Richard Pouyat told The New York Times. Pouyat measures worm populations by applying a solution of hot mustard in water to the ground. But it is also likely that a brief contact with hot peppers would not hurt the worms any more than it hurts the lips, he said, given that fishermen who collect worms using the hot-mustard method report that the worms live indefinitely after collection.
Compost worms are also selective feeders, Pouyat notes, so they are able to sense the presence of the burning element of hot peppers, capsaicin, before they eat any of it. Thus the survival capability of worms comes to the fore, as does the survival mechanism of the pepper plant itself in using a burning compound to ward off threats of eating by mammals. Hot peppers are not likely to kill a worm herd, as over time they break down into harmless compounds like other organic material. Still, red wiggler expert Bentley Christie of the Red Worm Composting website recommends avoiding adding hot peppers, and certainly not in any quantity, to the worm bin, as the worm's skin is a delicate organ. It's better to err on the side of caution, he indicates, and put the hot peppers in a regular compost pile.