Autumn 2017 EN

English Issue
Biogas Journal
| Autumn_2017
conventional biogas processes, the anaerobic sequencing
batch reactor (ASBR) used here offers significant
savings for operators using the energy they produce as
well as retention time in the digester specific to certain
substance groups, which results in considerably higher
yields. A similar plant for slaughtering waste was already
tested at BTU Cottbus.
“We were able to demonstrate that Pilgrims Pride could
cover its entire heat needs with a plant like this”, explains
Bravo de Sepúlveda. Now the company is making
plans in this direction because this is probably the only
way it will be able to meet the coming environmental
requirements. But there is not a specific time and financing
plan yet.
Violeta Bravo de Sepúlveda is already working on the
The Honda diesel motor is modified such that it runs on methane. It uses a V-belt
to operate the milking machine on the Rancho Sinai farm.
Cow dung collection area near the city of Queretaro. Trucks collect the dung from cattle
ranches in the area. It is not currently being used to generate energy, but is instead spread
as fertilizer on avocado farms.
next project. A biogas plant is supposed to be constructed
with feed producer La Perla; at a capacity of 100
million kilowatt hours per year, it will more than cover
the company’s entire heat needs. 185,000 tonnes of
manure, nearly 4,000 tonne of vegetable waste from
greenhouses, and large amounts of used grease and
whey are supposed to be fermented. This should reduce
methane emissions especially relevant to climate
change by 5,300 tonnes.
Among other issues, this project is investigating the
development of suitable logistics for transporting the
substrates as well as the technical challenges of fermenting
them together. Since January 2017, a biogas
test plant has been running in the institute laboratory
for this investigation. Violeta Bravo de Sepúlveda knows
that “used grease produces four times as much methane
as manure”.
A trip around the city of Querétaro gives an impressive
look at the region’s potential: The Agropark’s sea of
greenhouses gleams in the sun. Tomatoes and peppers
are grown here for the entire country. Not far away, the
legendary monolith Peña de Bernal sits at the horizon.
Every year on 21 March, crowds of esoterics gather at
the cliffs to take in their energy. But the true mountains
of energy rise before the cliffs, at the manure collection
spot.
Increasing food production and growing
mountains of waste
Long trucks tip their beds to unload what they have
collected at the cattle ranches in the area. Front loaders
shove and layer the brown mass into heaps as
tall as houses. The majority of the beef consumed in
Mexico is raised here in Ezequiel Montes. Currently,
the collected manure is still being used, untreated,
as fertilizer on avocado farms. Agriculture is a growing
industry in Mexico. And along with it, the amounts
of manure and organic wastes. For example, there are
already five million farms with about 18 million pigs.
Both food production and the generation of wastewater
and residential waste are also increasing. 82,000 litres
of wastewater are generated in Mexico every second.
And 100,000 tonnes of household garbage every day.
The Mexican government has made an obligation to
reduce the country’s greenhouse gas emissions by 30
percent, with respect to the level in 2000, by the year
2020, and by 50 percent by the year 2050. And the
use of methane for energy generation comes into play
here, also due to the drastic drop in the price of CO 2
certificates.
“Actually, this project should earn money by trading in
CO 2
certificates”. Rodolfo Montelongo points to three
thick, black cylinders used to burn off methane in a
controlled manner. They protrude into the blue sky over
the landfill site of San Nicolas in the state of Aguascalientes.
They were installed in 1998. Ten years later,
his employer, the British concern Ylem Energy, decided
to invest another five million U.S. dollars and use the
methane to generate electricity.
Electricity from landfill gas for Nissan
Since December 2011, two Caterpillar generators with
a total capacity of 2.4 megawatts have been feeding
electricity into the grid. Now the methane from the
landfill is only burned off if the generators are not working.
100 percent of the plant’s income comes from the
sale of electricity. The Japanese automobile manufacturer
Nissan, which runs its production in Mexico in the
Aguascalientes industrial park, purchases the 10 gigawatt
hours produced per year. Rodolfo Montelongo is a
not allowed to say how much Nissan pays per kilowatt
hour. Only that they pay less than the price for the in-
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