I recently have been thinking of a way to make the biofuel system better. I eventually came up with an idea - Maggots (Technically, they're actually some kind of compost worm, because maggots are fly larvae, but we'll just call them Maggots).
First, there would be a new block: the Compost Bin. In this bin, the player puts Maggots, Water, and different organic materials to compost. Maggots are not consumed. The bin works in cycles - first, the player inputs materials to compost, into a 2x2 grid - one item from each slot is taken (only one from each slot, up to 4 items total), and after the cycle is up, composted materials are output in the output slot, the number of them being the same as how many items were taken from the 2x2 grid.
The composted materials will also have a "quality" value - this is determined by the kinds of items thrown into the 2x2 grid, and the type of Maggots in the compost bin - more on that later. The average quality of all 4 (or less) items taken from the grid is the base quality value, multiplied by the maggots' quality modifier value.
Another block - the Fermenter - would take Composted Materials and make Biomass out of them. The amount of biomass created depends on the quality of the composted materials input into the fermenter. The biomass can be directly burned in a Semifluid Generator, or processed in another machine - the Distillery.
The Distillery is the only one of these three new machines that needs a kind of fuel. The basic one is slow and uses burnable fuels, and the electric one is faster, running on electric energy. The distillery takes Biomass, boils it, and creates from it Scrap and Biofuel. Biofuel, of course, can be burned for energy, just like in the current system.
Now, on to the Maggots. Maggots would be put into a Maggot Bin to breed. They would just be a pile of Maggots, having different traits and all. There are 2 input slots in the maggot bin - both for different maggots to be put in and to breed. If only one slot is filled, after a while, they will produce Offspring, but at a slower rate than breeding two kinds of maggots. The traits of the maggots that breed will combine, like with forestry bees, and have a small chance to combine to form a better, more refined/desirable trait. Those desirable traits would affect the maggot quality, fertility, work rate, etc.
To obtain maggots, the player can kill Zombies. They would rarely drop a pile of maggots with basic, common traits (biome dependent?). In the nether, zombie pigmen would rarely drop maggots with more desirable traits.
Some exotic kinds of maggots could even be able to process different kinds of materials to create different stuff - like processing Crushed Ores slowly into more dusts than normal, or processing Redstone/glowstone directly into Energy, more efficiently than just throwing Redstone into an energy storage block.
An even more endgame type of maggot, would possibly be able to make Super Composted Materials, which are fermented into Super Biomass, which is distilled into Fertilizer and Superfuel. These would be very difficult to get, though, and would require using the maggot breeding process to obtain them, rather than just finding them.
Just like all other suggestions, I want your feedback. Tell me what you like/dislike about this idea, and how it can be improved. It is much better to propose to the developers a more refined idea, rather than what I just thought up. I also included a Poll, to make it easier to see how many support/don't support this idea. Thank you.