Beyond the Cone: Extracting Value from Hop Leaf Waste

Commodities

Practices

Small hop farms across the north-central region face a common challenge: 35% to 50% of the hop plant, its leaves, has no established market value. While hop cones are highly sought over, leaf material obtained during harvest is typically discarded, composted, or burned.

However, hop leaves contain visible oil glands. Glands that are structurally similar to those found in the cones. If these oils can be extracted and utilized, they could represent an added income opportunity for small farms.

In nature, these leaf oils function as defenses against insect feeding. European trials have shown that certain native hop species (but not modern commercial cultivars) discourage insects from feeding on berries and certain mosquitoes from feeding on humans.

Growers currently lack data on whether hop leaves can provide consistent, usable oil and if cultivar choice or basic processing steps influence yield or quality. This project addresses that gap by evaluating whether hop leaves can be transformed from an agricultural waste product into a viable value-added ingredient and/or natural pest-management tool, creating new revenue potential for North Central hop growers.

Extraction Method

Traditional plant extraction methods are often energy-intensive and wasteful. Hydrocarbon-based solvent extraction, using butane or propane, dissolves oils but poses fire hazards and may leave in residual solvents. Supercritical CO₂ extraction is solvent-free, but requires expensive high-pressure equipment and can release substantial gas. Steam, while inexpensive, is not suitable for hops oil because heat degrades key aromas, producing cooked, off-flavors.

Our approach uses supercooled water. On the plant, hop oil is stored in small yellow external lupulin glands. These glands solidify at low temperatures and can be mechanically dislodged. Glands are collected from near-freezing water, dried, and sold as highly concentrated hopping reagents. Water is the only extraction ingredient, cycled through a chilling system. This method reduces energy use, avoids solvents, preserves compounds, and minimizes waste, making it both cost-effective and environmentally friendly

Repellent and Irritant Effects

Hop oils naturally deter several pests. Research shows activity against wheat weevils, Drosophila suzukii, Anopheles mosquitoes, and the parasitic honey-bee mite. Our 2025 field observations demonstrated differences in herbivory among hop genotypes: North Central native hops experienced only 4.8 ± 2.42% leaf damage, while the Newport cultivar from the Pacific Northwest suffered 21.1 ± 2.09% damage under the same conditions. These differences suggest that leaf-oil composition or concentration contributes to insect deterrence. This is consistent with European research showing native hops repel pests more effectively than imported cultivars.

This project will test whether extracted hop leaf oil can reduce feeding/oviposition on other crops. By pairing extraction data with controlled bioassays, we aim to determine if leaf oils can serve as practical, plant-derived repellents for broader agricultural use

Project Approach

We will separate oil glands from hop leaves and cones of native plants and evaluate:

Chemical composition and yield: Flavor components (α- and β-acids) will be quantified via high-performance liquid chromatography (HPLC), and aroma compounds (terpenes and terpenoids) via gas chromatography with flame ionization detection (GC-FID), conducted with industry partner AAR Labs (Madison, WI).

Brewing potential: Partner brewers will assess aroma, flavor, and suitability for beer production, with feedback collected via sensory evaluation score sheets.

Insect-repellency potential: Repellency will be evaluated using a randomized block, treatment-control design. Raspberry and elderberry plants will receive either no treatment (control) or 10 g of concentrated hop leaf-derived powder per plant (rate informed by European trials). Pest presence, feeding/oviposition, and fruit damage will be monitored in field trials to assess effectiveness

Impact

This project converts a currently discarded material into a potential dual-use product:

1. A concentrated, potentially terroir-distinct brewing ingredient.
   
   
2. A natural pest repellent suitable for organic, IPM, and small-farm systems.
   
   

By providing data on extraction, chemical composition, brewing potential, and pest repellency, the project will help North Central growers turn hop leaf biomass from waste into a value-added resource.