Apple pomace is wet and compact.  If not well mixed with stiff, absorbent material, large clumps of this or other fruit wastes can become airless regions of anaerobic decomposition.  Having a high water content can be looked upon as an advantage.  Dry hay and sawdust can be hard to moisten thoroughly; these hydrate rapidly when mixed with fruit pulp.  Fermenting fruit pulp attracts yellow jackets so it is sensible to incorporate it quickly into a pile and cover well with vegetation or soil.

The watery pulp of fruits is not particularly rich in nutrients but apple, grape, and pear pulps are generously endowed with soft, decomposable seeds.  Most seeds contain large quantities of phosphorus, nitrogen, and other plant nutrients.  It is generally true that plants locate much of their entire yearly nutrient assimilation into their seeds to provide the next generation with the best possible start.  Animals fed on seeds (such as chickens) produce the richest manures.

Older books about composting warn about metallic pesticide residues adhering to fruit skins.  However, it has been nearly half a century since arsenic and lead arsenate were used as pesticides and mercury is no longer used in fungicides.

Bagasse is the voluminous waste product from extracting cane sugar.  Its C/N is extremely high, similar to wheat straw or sawdust, and it contains very little in the way of plant nutrients.  However, its coarse, strong, fibrous structure helps build lightness into a pile and improve air flow.  Most sugar mills burn bagasse as their heat source to evaporate water out of the sugary juice squeezed from the canes.  At one time there was far more bagasse produced than the mills needed to burn and bagasse often became an environmental pollutant.  Then, bagasse was available for nothing or next to nothing.  These days, larger, modern mills generate electricity with bagasse and sell their surplus to the local power grid.  Bagasse is also used to make construction fiberboard for subwall and insulation.

Banana skins and stalks are soft and lack strong fiber.  They are moderately rich in phosphorus, potassium, and nitrogen.  Consequently they rot quickly.  Like other kitchen garbage, banana waste should be put into the core of a compost pile to avoid attracting and breeding flies.  See also:  Garbage.

Basic slag is an industrial waste from smelting iron.  Ore is refined by heating it with limestone and dolomite.  The impurities combine with calcium and magnesium, rise to the surface of the molten metal, and are skimmed off.  Basic slag contains quite a bit of calcium plus a variety of useful plant nutrients not usually found in limestone.  Its exact composition varies greatly depending on the type of ore used.

Slag is pulverized and sold in sacks as a substitute for agricultural lime.  The intense biological activity of a compost pile releases more of slag’s other mineral content and converts its nutrients to organic substances that become rapidly available once the compost is incorporated into soil.  Other forms of powdered mineralized rock can be similarly added to a compost pile to accelerate nutrient release.