Potential Reuse of Waste Coffee Grounds considers using the significant amount of waste coffee grounds (WCG) generated annually from coffee consumption as a feedstock for biodiesel production and other applications. WCG contains 10-20% oil that can be extracted for conversion to biodiesel, with the residual grounds used as a purification material in biodiesel production or as an alternative fuel source. While research is still ongoing, utilizing WCG in the biodiesel industry and for power generation could help divert WCG from landfills while reducing biodiesel production costs and providing economic opportunities.

1. Potential Reuse of Waste Coffee
16 em march 2013 awma.org
Copyright 2013 Air & Waste Management Association
em • feature
This article considers the potential for the waste byproduct of one of the world’s most popular
beverages—used coffee grounds—to be diverted from landfills and repurposed as an oil basis
for biodiesel fuel, a purification material, and an alternative energy source.

2. Coffee is one of the most popular beverages in the
world. Each day, more than 2.25 billion cups of
coffee are consumed globally.1 In the United States,
the average coffee consumption in 2008 was
24.2 gallons per person. Although there are more
than 70 coffee species, the current coffee market is
dominated by two types of coffee species: Arabica
and Robusta.2 The preparation of commercial coffee
products starts with processing coffee cherries, the
raw fruit of coffee plant, into green coffee beans.
The next step is roasting that converts green beans
into brown beans. Roasting process gives the char-acteristic
aroma and flavor to the coffee brew,
which is dependent on the temperature and reten-tion
awma.org march 2013 em 17
Copyright 2013 Air & Waste Management Association
time of the roasting process.2-4
WCG Inventory, Properties,
and Current Uses
Coffee consumption leads to the generation of
waste coffee grounds (WCG). Accordingly to the
International Coffee Organization (www.ico.org), in
2010, the net coffee consumption (both roast and
instant) by the United States was 1.31 million tons
(2.61 billion lbs).5 The market share for roast coffee
is estimated at 80%.6 Therefore, the WCG gener-ated
in the United States is estimated at 1.05 mil-lion
tons (2.10 billion lbs) per year. This significant
amount of WCG generation every year results in
multiple environmental and ecological concerns,
such as landfill expansion, and water and soil quality
deterioration due to leachate.7
The composition of WCG is mainly constituted
by cellulose, hemicelluloses, minerals, sugars, oils,
polyphenols, and ashes.2,8 Concentration and com-position
of oil in WCG have been explored by
several studies.9-11 In most cases, oil concentration
ranges from 10–20 wt%. It is reported that the oil
content in the coffee bean changes negligibly
during the roasting and brewing processes and it is
reasonable to assume that the oil concentration in
the WCG remains close to that of the original cof-fee
cherries.2,3 Besides, the composition studies also
show that oil from WCG mainly consists of long
oxygenated carbon chains, such as C16:0, C18:0,
C18:1, and C18:2. Elemental analysis shows that
WCG contains mainly carbon (C), oxygen (O), and
hydrogen (H), with minor portions of sulfur (S),
phosphorus (P), and potassium (K).12,13 The size of
the WCG varies with different grinding processes
and its structure is porous by nature.
Currently, most of the WCG from cafeteria, restau-rants,
and households are discarded and end up
in landfills. Several pathways of direct reuse have
been advocated for the reuse of WCG in daily life,
such as odor and pest control media, gardening
and composting materials, and furniture care
(scratch cover).14 Using WCG as the growth media
for certain types of fungi is another alternative of
interest.2 Considering its porous nature, WCG has
been studied as the substrate for activated carbon
(AC) preparation and tested for removal of various
chemicals and pollutants.12,15,16
WCG Applications in
the Biodiesel Industry
The composition of the oil in WCG has attracted
interest from researchers to find a use for it in the
biodiesel field. This application, once commercial-ized,
has the potential to reuse WCG in large quan-tities,
considering the huge biodiesel production
by Qingshi Tu,
Mingming Lu,
and Ming Chai
Qingshi Tu and
Mingming Lu are both
with the School of Energy,
Environmental, Biological,
and Medical Engineering,
University of Cincinnati,
Cincinnati, OH. Ming
Chai is with Bluegrass
Biodiesel, Falmouth, KY.
E-mail: tuqi@uc.edu.
Grounds in the Biodiesel Industry

3. Guideline on Air Quality Models: The Path Forward
March 19-21, 2013
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grounds after extraction) to bring revenue to the
entire supply chain.
One option for the after-extraction WCG is to be
used as biodiesel purification material. Biodiesel
purification is shifting away from the traditional
water wash to “dry wash” approaches, which elimi-nate
water consumption and wastewater generation.
Adsorbents and ion-exchange resins have been
applied by many biodiesel producers. Depending
on the process and the quality of crude biodiesel,
the dry wash can cost the biodiesel producer
anywhere from 10 cents to 50 cents per gallon
of biodiesel.17
From our preliminary study, the after-extract WCG
demonstrated comparable purification capability to
existing commercial products, which indicates the
possibility of reducing costs by applying WCG for
purification purposes after its usage in biodiesel
production. The replacement of commercial purifi-cation
materials with WCG can reduce the overall
production costs of biodiesel and also lower the
uideline y M
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Guideline on Air Quality Models: The Path Forward will provide a
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Environmental Protection Agency's Guideline on Air Quality Models,
the guideline that is required for use in the preparation of state
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Sponsorship and Tabletop Opportunities are available! For details
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every year. The utilization of WCG as the feedstock
can significantly lower the cost of biofuel produc-tion
and reduce the use of food crops. Converting
coffee oil into biodiesel has been widely studied
and, in most cases, the production is divided into
two steps: oil extraction by either organic solvent or
supercritical carbon dioxide (CO2) and transester-ification
of the resulting oil into biodiesel.10,11
Solvent extraction is a tough sell to the biodiesel
industry, so further research and development is
needed to search for alternative approaches. For
the current two-step process (extraction then con-version),
it is imperative to find valued-added path-ways
for the residual materials (i.e., the coffee
Although there are more than 70 coffee species, the current
coffee market is dominated by two types of coffee species:
Arabica and Robusta.2
18 em march 2013 awma.org
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ch th C

4. waste disposal expenses, since it can be burned as
adjunct fuel afterward instead of being sent to a
landfill, which is the normal practice for the
commercial purification materials after use.18
It was found from our preliminary experiment that
WCG possessed a heating value of 8,795 Btu/lb.
WCG has also been tested as the alternative fuel at
a power plant in Japan.19 The results from a life
cycle assessment study on burning WCG as solid
biomass substrate also showed that combustion of
1 kg of WCG in municipal incinerator can gener-ate
0.53 kWh electricity and 3.92 MJ of useful
heat.20 So, considering its energy potential, WCG
can also serve as a cost-saving option for power
generation after it accomplishes its roles as oil
source and purification material.
One of the major challenges is how to collect the
WCG from individual homes and stores. For WCG to
achieve its full potential as an alternative energy
source, the separation of WCG from the rest of
landfill wastes and educating the public on its pos-sible
uses will be necessary.
Summary
As one of the world’s most consumed beverages,
the prosperity of the coffee industry leaves behind
a significant amount of WCG every year. The tra-ditional
disposal of WCG into landfills should be
revisited. Considering the properties of WCG, it is
possible to include it into the biodiesel industry
by extracting the coffee oil and making it into
biodiesel. Using after-extraction WCG as a purifi-cation
material and an adjunct fuel may then
reduce the overall cost of WCG-derived biodiesel.
Although most of the activities in this reuse path-way
are still at the research and development stage,
the technology development and the increased
awareness of sustainability are expected to boost
the commercialization of the research outcomes in
the near future. em
References
1. Ponte, S. The “Latte Revolution”? Regulation, Markets, and Consumption in the Global Coffee Chain; World Development 2002, 30, 7, 1099-1122.
2. Mussatto, S.I.; Machado, E.M.S.; Martins, S.; Teixeira, J.A. Production, Composition, and Application of Coffee and Its Industrial Residues; Food
awma.org march 2013 em 19
Copyright 2013 Air & Waste Management Association
Bioprocess 2011, 4, 661-672.
3. Wang, N. Physicochemical Changes of Coffee Beans during Roasting; MS Thesis, University of Guelph, Guelph, Ontario, Canada, 2012.
4. Chemical Changes during Roasting. See www.coffeechemistry.com/index.php/Roasting/General/chemical-changes-during-roasting.html
(accessed December 2012).
5. U.S. Coffee Sector; International Coffee Organization, 2010; available at www.ico.org/countries/usa.pdf (accessed December 2012).
6. Purcell, D. The Coffee Grind; specialtyfood.com, 2010; available at www.specialtyfood.com/news-trends/featured-articles/article/coffee-grind/
(accessed December 2012).
7. Chanakya, H.N.; De Alwis, A.A.P. Environmental Issues and Management in Primary Coffee Processing; Process Safety and Environmental
Protection 2004, 82, 291-300.
8. Mussatto, S.I.; Carneiro, L.M.; Silva, J.P.A.; Roberto, I.C.; Teixeira, J.A. A Study on Chemical and Constitutes and Sugars Extraction from Spent
Coffee Grounds; Carbohydrate Polymers 2011, 83, 368-374.
9. Al-Hamamre, Z.; Forester, S.; Hartmann, F.; Kroger, M.; Kaltschmitt, M. Oil Extracted from Spent Coffee Grounds as a Renewable Source for
Fatty Acid Methyl Ester Manufacturing; Fuel 2012, 96, 70-76.
10. Couto, R.M.; Fernandes, J.; Gomes da Silva, M.D.R.; Simões, P.C. Supercritical Fluid Extraction of Lipids from Spent Coffee Grounds; J. Supercritical
Fluids 2009, 51, 159-166.
11. Kondamudi, N.; Mohapatra, S.; Misra, M. J. Spent Coffee Grounds as a Versatile Source of Green Energy; Agricultural Food Chemistry 2008,
56, 11757-11760.
12. Azouaou, N.; Sadaoui, Z.; Djaafri, A.; Mokaddem, H. Adsorption of Cadmium from Aqueous Solution onto Untreated Coffee Grounds: Equilibrium,
Kinetics, and Thermodynamics; J. Hazardous Materials 2010, 184, 126-134.
13. Tu, Q. Assessment of Selected Sustainability Aspects of Biodiesel Production: Water and Waste Conservation; MS Thesis, University of Cincinnati,
Cincinnati, OH, USA, 2012.
14. 11 Reuse Ideas for Coffee Grounds. See http://myzerowaste.com/2010/01/11-reuse-ideas-for-coffee-grounds (accessed December 2012).
15. Kante, K.; Nieto-Delgado, C.; Rangel-Mendez, J. R.; Bandosz, T.J. Spent Coffee-Based Activated Carbon: Specific Surface Features and Their
Importance for the H2S Separation Process; J. Hazardous Materials 2012, 201-202, 141-147.
16. Castro, C.S.; Abreu, A.L.; Silva, C.L.T.; Guerreiro, M.C. Phenol Adsorption by Activated Carbon Produced from Spent Coffee Grounds; Water
Science & Technology 2011, 64 (10), 2059-2065.
17. Sims, B. Finding the Right Purification Approach, 2011; available at www.biodiesel magazine.com/articles/7661/finding-the-right-purification-approach
(accessed January 2013).
18. Tu, Q.; Lu, M.; Chai, M. Beneficial Use of Waste Coffee Grounds as Feedstock and Purification Material for Biodiesel Production. Presented at
A&WMA’s 105th Annual Conference & Exhibition, San Antonio, TX, June 18-22, 2012.
19. Coffee Grounds Give Jolt to Crippled Japanese Energy Grid; abcnews.com, 2011; available at http://abcnews.go.com/Business/coffee-grounds-supply-
power-japan-shuts-nuclear-plants/story?id=13770412#.T6FM-Xg3_Ko (accessed December 2012).
20. ESU-Services Ltd. Life Cycle Assessment of Burning Different Solid Biomass Substrates, 2011.
Considering its
energy potential,
WCG can serve
as a cost-saving
option for power
generation after it
accomplishes its
roles as oil source
and purification
material.