Concept of Waste to Energy

Topics: Anaerobic digestion, Sewage treatment, Water pollution Pages: 19 (3889 words) Published: March 10, 2013
The Concept of Wastes to Energy
Using Sugary Wastes
Fiza Sarwar, Wajeeha Malik, Muhammad
Salman Ahmed, and Harja Shahid
Fiza Sarwar

Wajeeha M.

M. Salman A.

Abstract: ThisstudywasdesignedusingactualeffluentfromthesugarymillsinanUp-flowAnaerobicSludgeBlanket (UASB)Reactortoevaluatetreatabilityperformance.Thereactorwasstarted-upinstep-wiseloadingratesbeginning from 0.05kg carbon oxygen demand (COD)/m3-dayto3.50kg-COD/m3-day.Thehydraulicretentiontime(HRT) wasslowlydecreasedfrom96hrstoeighthrs.ItwasobservedthattheremovalefficiencyofCODofmorethan73% can be easily achieved at an HRT of more than 16 hours corresponding to an average organic loading rate (OLR) of3.0kg-COD/m3-day,atneutralpHandconstanttemperatureof29oC.TheaverageVFAs(volatilefattyacids)and biogasproductionwasobservedas560mg/Land1.6L/g-CODrem-d,respectively.Theaveragemethanecomposition wasestimatedas62%.Theresultsofthisstudysuggestthatthetreatmentofsugarmillseffluentwiththeanaerobic technology seems to be more reliable, effective and economical. Key words: Anaerobic digestion, sugary wastes, carbon oxygen demand, biogas, Pakistan


Pakistan is a water deficient country; the quantity of
available water resources has been declining day by day.
In 1960 it was 5654m3/capita, by 2000 it was 1400m3/
capita and by 2010 the capacity was expected to be
1000m3/capita (Ali, Hashmi et al 2009). The water
quantity (flow rate) is decreasing day by day due to such
factors as temperature, atmospheric pressure, wastage
due to improper management, and pollution.
The available water in Pakistan is being polluted at an
alarming rate, mainly due to untreated domestic and
industrial effluents and agricultural/surface runoffs,
etc. Domestic effluent includes sewage as well as sludge
while industrial effluents only include waste sewage. The
runoffs may include garbage and sediments. Due to all
these effects of pollution, the only clean and potable water available is 18% and the remaining 82% is unfit for drinking purpose.
Besides water deficiency it is a known fact that Pakistan
is deficient in energy, though it has a substantial potential of energy. The energy is not confined only to electrical energy, but bio-gas has also a significant share in this sector. However, bio-gas has not been given the attention it deserves. Biomass is an important resource in Pakistan, about 37% of total primary energy supply. The

growing acceptance of anaerobic digestion at a simple,
low-cost high rate and effective waste treatment technology make it a viable solution for pollution control, in addition to give support to energy resources sector. The sugar industry plays an important role in the nation’s economy. Progress in technology has been made by this industry. At the time of the Independence there

were only two sugar mills, one at Rahwali in the Punjab
and the other at Takhat Bai in the Khyber Pakhtun Khwa
(KPK). The total quantity of sugar produced during 194748 was 7,932 tons. Today there are 75 sugar mills all over HYDRO NEPAL


JULY, 2011

the country. The majority of these mills are based on
sugar cane. The total crushing capacity of this industry is
approximately 3.0 million tons per day.
By comparison, only four mills process beets for sugar
Molasses is a byproduct of the sugar manufacturing process and is exported to other countries. In Pakistan seven sugar mills convert a part of their molasses into industrial alcohol. Pakistani sugar mills rarely exploit the possibilities of

reusing wastes in the process, or as by-products. A considerable development of sucrochemistry and ethanol applications is expected in the near future. This development will bring forth problems to a scale (especially associated with pollution by aggressive molasses and

vinasses) that makes the current problem appear...
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