Almond Hulls

As the almond fruit matures on the tree it dries, and the hull splits along a suture to expose the shell inside. Harvest brings down the whole dried fruit, and hulling is the first operation at the processor: the hull is separated mechanically from the shell, before any shelling takes place. What comes off is a light, dry, fibrous material carrying residual sugars from the fruit flesh.

Almond hulls are fed to ruminants, most prominently in dairy rations in the regions where almonds are grown at scale. They carry digestible fibre and residual sugars in a combination that suits a ruminant, and they are palatable — a genuine feed material rather than a filler. Because they are already dry, they store and transport like other dry feed ingredients rather than demanding the immediate drying or ensiling that wet residues do.

Composition is not uniform. Hulls from different cultivars differ in sugar and fibre, and how cleanly the huller separates hull from shell determines how much shell fragment ends up in the hull stream — shell being fibrous, indigestible, and a straightforward dilution of feed value. Hull lots are therefore specified partly on how little shell they contain, and the huller's separation efficiency is directly visible in the by-product's value.

Beyond feed, hulls are used as a bedding and mulch material, as a substrate for mushroom growing, and as a feedstock for energy recovery and composting. Research interest in higher-value routes — extracting sugars for fermentation, or recovering functional compounds — reflects the fact that the volume available exceeds what the feed market can absorb in a strong production year.

Handling is straightforward by by-product standards. Hulls are bulky and low in density, which drives transport cost rather than spoilage risk, and they are commonly stored in the open. They are hygroscopic and will take up moisture and mould if allowed to wet, and their residual sugar makes them attractive to insects and vertebrate pests in storage — the practical concerns are these rather than the rapid fermentation that governs wet residues.

• Feed — ruminant rations, particularly dairy, the dominant outlet
• Bedding and mulch — livestock bedding and orchard mulch
• Industrial — mushroom growing substrate and fermentation feedstock
• Energy — biomass fuel and digester feedstock