Works to Retain Nitrogen, Control Odor, and Improve Poorly Structured Soils.

photo of Compost Sugar product commercial composting operations can buy Compost Sugar in bulk finished pumice-enhanced compost

Compost Sugar™ is an economical pumice mine grade, sold by bulk ton, ideal for commercial and agricultural composting operations. It is also available in 45 lb production bags for bespoke composting.


A One-Two Punch Amendment

Not only do pumice and composting belong in the same sentence, they belong in the same organic-waste-to-blackgold process—and the same soil-improvement calculation. Blended with organic feedstock, Compost Sugar™ (a pumice grade-blend) tamps down decomposition volatility, then combo-punches with the finished compost to rebuild and recharge poorly-structured, nutrient-starved junk soils.

One: Pumice Sweetens the Decomposition Process

Blending organic feedstock with pumice improves the composting process itself, as pumice buffers the extreme volatilization cooking off in the decomposing matter, capturing nitrogen and mitigating its loss. Pumice also provides inert bulk that improves airflow and process efficiency, especially when composting soft manures.

The following studies show the viability of pumice as an amendment to the composting matter to sweeten the overall process and better meet the challenges of various feedstocks.

VOC REDUCTION: A study published in Biosource Technology1 detailed research using natural material amendments blended at a 1:10 volumetric ratio with poultry litter to reduce Volatile Organic Compounds (VOCs) during composting. The results (at 100 days) quantified the effectiveness of pumice to reduce VOCs at an impressive rate—an 88% reduction. Pumice out-performed the other materials tested.

MITIGATING NITROGEN LOSS: A study2 done by an environmental engineering department in a Turkish university looked at improving nitrogen availability in composted poultry litter (mitigating NH3 volatilization) using natural amendments—including pumice. The study showed blending natural materials significantly reduced NH3 volatilization. In particular, only 26% of initial total N was lost from the compost blended with pumice.

EFFECTIVE BULKING AGENT: Bulking agents can reduce the cost, labor, time duration, and increase the compost quality and nutritive values. The choice of bulking agent is dictated by what is being composted. For wet materials, a low-moisture, highly absorbent amendment like pumice fits the need.

A Chinese study3 quantified the contributions of pumice in sewage sludge composting when used as an inert bulking agent. Pumice, with its rich pore structure and strong water absorbent capacity, was found to significantly improve the biological reactions in the composting process in terms of material porosity, water-holding capacity, nitrogen absorption (promoting ammonia assimilation to organic nitrogen rather than loss to volatilization), and acceleration of the composting period.

As an inert composting amendment agent, pumice avoids the drawbacks of using organic bulking agents—straw, husks, wood chips, sawdust—as pumice does not breakdown nor compact during the composting process. Pumice performs consistently, blends readily, and is easily sourced and stored. The physical foamed-stone character of pumice also provides an ideal carrier for adding additional elements to the bio-formulation, such as sucrose3 (to add a carbon source and provide a growth platform to quickly ignite microbial action).

Two: Pumice Gives Compost Bones

Compost is valuable for both the nutrient charge that it adds to poor or depleted soils and for the (temporary) physical reshaping it brings to the soil structure itself. A friable, well-composed root zone is vital to sustained vegetative health, and composted organic matter certainly lends those structural benefits to poorly-structured soils...until it doesn’t. Once the organic matter is exhausted, poorly-structured soils collapse, reverting to inglorious junk-dirt status. The solution: compost fortified with inorganic bones.

Reconditioning the soil every few years with a fresh stir-in of compost is doable in an annually remade garden or flowerbed, but for landscaping and turf projects, construction/mining reclamation or runoff-controlling bioswale constructs, a permanent solution to poorly structured soils is vital to long-term success. Pumice-blended compost meets that need.

The frothy-stone form factor of pumice—from the smallest particle to the largest—brings a muscular physical element to structure-poor soils. The Compost Sugar™ grade-blend lightens soil texture, resists compaction, improves drainage and aeration, moderates soil temperature, enhances pore space, retains moisture—and does so indefinitely, interlocking with the soil particles and staying there.

PUMICE-AMENDED SOIL PERFORMANCE QUANTIFIED: The Journal of Central European Agriculture (2005) published a study4 that measured strawberry seedling growth in pumice-amended soil, quantifying an “important level” increase in growth and attributing that growth to the enhanced moisture retention and improved pore size distribution imposed by the pumice.

Another study5 concluded “that pumice may be effectively used in specific amounts for improving aeration and bulk density conditions of poorly structured soils.”

A study6 published in the Australian Journal of Crop Science focused on adding pumice to achieve gains in soil moisture absorption and retention for maize (corn) crops. The results? “Pumice significantly increased the amount of soil moisture retention compared to control. Growth characteristics of maize (vegetative growth and yield) were significantly improved with increasing amount of pumice concentration.”

Economical to Source

Pumice is an abundant volcanic material found in extensive deposits world-wide—like the Hess Pumice deposit in Southeast Idaho, USA. Compost Sugar™ is a minimally-processed mine grade blend from the Hess deposit, naturally pure and economical to source. Compost Sugar is available in bulk, shipped directly from the mine, or available packaged in 2000 lb supersacks or in 45 lb production bags for bespoke composting operations.


Technical Data Sheets: the physical and chemical properties of pumice from the Hess deposit is found on page two of the Compost Sugar TDS document, linked in the order blocks below).

SDS: Pumice Safety Data Sheet (PDF).

Certificate: Non-Expiration (PDF).

Declaration: Non-Crystalline Silica (PDF).


[1] Removal of Volatile Organic Compounds by Natural Materials During Composting of Poultry Litter. (Bioresource Technology, 2008) Department of Environmental Engineering, Ondokuz Mayıs University, Samsun, Turkey; by N.G. Turan, A. Akdemir, O.N. Ergun.

[2] Nitrogen Availability in Composted Poultry Litter Using Natural Amendments. Department of Environmental Engineering, Ondokuz Mayis University, Samsun, Turkey; by N. Gamze Turan. Waste Manag Res. 02/2009.

[3] Usage of Pumice as Bulking Agent in Sewage Sludge Composting. (Bioresource Technology, 2015) Harbin Institute of Technology, Harbin 150090 & School of Environment, Henan Normal University, Xinxiang 453007, China; by Chuandong Wu, Weiguang Li, Ke Wang, Yunbei Li.

[4] Effect of Pumice Amendment On Physical Soil Properties and Strawberry Plant Growth. Ustun SAHIN, Selda ORS, Sezai ERCISLI, Omer ANAPALI, Ahmet ESITKEN; Atatürk University, Department of Agricultural Structures and Irrigation, Erzurum-Turkey

[5] Addition of Pumice Affects Physical Properties of Soil Used for Container Grown Plants. Ustun SAHIN, Omer ANAPALI; Agriculturae Conspectus Scientificus (ACS) 01/2006; 71(2)

[6] Soil Water Retention and Maize (Zea mays L.) Growth as Effected by Different Amounts of Pumice. Ashraf Malekian, Einollah Valizadeh, Mona Dastoori, Sohaila Samadi, Vahid Bayat; Department of Agriculture, Payame Noor University, PO Box 19395-3697, Tehran, Iran