Chemical Engineering January 2018 - 7

Waste coffee grounds are used
to make biodiesel blend
A
P
biodiesel fuel blend known as B20
contains oils derived from waste
coffee grounds, and will be used to
power mass transit buses in London.
The fuel is made through a partnership
among bio-bean ltd. (London, U.K.;
www.bio-bean.com), which has developed
a process for extracting useful oils from
waste grounds, biodiesel producer Argent
Energy and Royal Dutch Shell.
The B20 biofuel is made by combining oil
from the waste coffee grounds with other
recycled waste fats and oils, and blending
that with mineral diesel fuel. Because recycled
waste oils, including the coffee oil,
makes up 20% of the B20 biofuel, it is 85%
more carbon efficient than standard diesel
and achieves a 10-15% CO2 reduction
over standard diesel.
Bio-bean works with waste management
partners to collect waste coffee grounds
from coffee chains, independent coffee
shops, transport hubs, office blocks and instant
coffee factories. The grounds are dried
and processed at bio-bean's Alconbury factory,
before a specialized solid-liquid extraction
process is used to isolate the oils from
the waste grounds. The solvent is fully recovered
and recycled, bio-bean says.
Argent Energy blends this coffee oil with
other biologically derived fats and oils and
then combines this mixture with mineral
diesel to create a B20 blended biofuel. The
fuel is then supplied directly into the London
bus network. With Shell's help, biobean
and Argent Energy have produced
6,000 L of pure coffee oil, enough to produce
30,000 L of B20 biofuel.
A photocatalyst for reducing CO2 to CH4
hotocatalytic reduction of CO2
into a fuel is an attractive way to
reduce CO2 emissions into the
atmosphere, and there are many
projects underway around the world to
find ways of converting CO2 into chemicals,
such as H2, CH4, ethanol, methanol
and butanol. However, in order to utilize
CO2 as a resource, it is essential to improve
the light-absorption efficiency and
the CO2-conversion efficiency, and to ensure
that the photocatalyst helps prevent
the production of secondary harmful substances.
Although a number of active photocatalysts
have been reported, they suffer
from low product yield, instability and low
quantum efficiency.
Now a team from the Daegu Gyeongbuk
Institute of Science and Technology
A
team from the National University
of Singapore (www.nus.
edu.sg) led by professor Boon
Siang Yeo has developed a
prototype device that mimics natural
photosynthesis to produce ethylene
using only sunlight, water and CO2, at
room temperature and pressure.
The team designed a two-electrode
cell and optimized cell parameters
such as electrolyte and voltage.
A photovoltaic cell is first used
to convert solar energy to electricity,
and the electricity powers the electrolyzer
to produce substances from
(DGIST, Daegu, South Korea; https://
en.dgist.ac.kr), led by professor Su-Il In,
has succeeded in developing a TiO2based
high-efficiency photocatalyst that
converts CO2 to CH4 by means of a
simple reduction reaction. The catalyst is
made by treating TiO2 with a strong reducing
agent - sodium borohydride (NaBH4)
- at 350°C for half an hour.
Sensitized with Pt nanoparticles, the
material promotes solar spectrum photoconversion
of CO2 to CH4 with an apparent
quantum yield of 12.40% and a timenormalized
CH4-generation rate of 80.35
µmol/g.h. Professor In says to the best of
his knowledge this is a record for photocatalytic-based
CO2 reduction. He plans
to further improve the CO2-conversion efficiency
with a view to commercialization.
Making ethylene by artificial photosynthesis
CO2 to H2O. The team used oxidederived
copper as electrocatalyst
in the cathode and iridium oxide as
electrocatalyst in the anode. Coupling
the cell with silicon solar panels under
sunlight (100 mW/cm2), the team
showed that CO2 could be easily reduced
to ethylene with an efficiency
of 31.9%, when operating the system
with a partial current density of
6.5 mA/cm2. Under these conditions,
the overall photosynthetic efficiency
(solar-to-ethylene) was 1.5%, but this
could be increased to 2.9% by the
addition of ethanol and n-propanol
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JANUARY 2018
to the system. The introduction of insoluble
chelating agents in the electrolyte
improved the longevity of the
cell, by capturing contaminants, such
as dissolved iridium ions.
A prototype system incorporates
a battery, which stores excess solar
energy, thereby enabling the stable,
continuous production of ethylene.
The team believes its work has
helped solve many problems associated
with the implementation of an
artificial photosynthesis system and
represents a major step forward in
the field of solar energy utilization.
7
tors who use the facility to
gain practical hands-on experience
in preparation for
their field work. The trainees
are from the Nobel Peace
Prize-winning Organization
for the Prohibition of Chemical
Weapons (The Hague,
the Netherlands).
FLOWER POWER
Researchers at Karlsruhe
Institute of Technology (KIT;
Germany; www.kit.edu)
have discovered that the texture
of the viola petal (Viola
wittrockiana) drastically
reduces reflection losses.
In nature, this effect leads
to a bright and saturated
color impression, which
the flowers use to attract
possible pollinators, says
KIT. The researchers have
demonstrated a 6% relative
improved performance of a
silicon solar cell by mimicking
the viola as front-side
texture. The results are described
in ACS Photonics.
Analysis of the surface texture
of the viola flower reveals
that it exhibits a hierarchical
texture consisting of cones
(on the order of tens of micrometers)
and nanoscopic
wrinkles adorned on top of
the cones. This hierarchical
texture is able to efficiently
increase light incoupling
when used as coating on
top of solar cells. In addition,
it reduces the loss of light at
the interface between the
encapsulation and the solar
cell, by redirecting escaping
light. According to the scien(Continues
on p. 8)
http://www.bio-bean.com http://www.kit.edu http://https:// http://en.dgist.ac.kr http://www.nus http://www.edu.sg http://WWW.CHEMENGONLINE.COM
Chemical Engineering January 2018

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