Zero The Discharge Brewery
Derek Kichula, Brian Gray, and Meredith Harvill Biological Systems Engineering, Virginia Tech
Introduction
Beer breweries waste byproducts include an abundance of spent grains, an unbalanced ratio of wastewater to beer produced, and harmful CO2 emissions, which are typically left untreated.
Waste Products
CO2 Recapture System
Large amounts of CO2 are released during the fermentation process. In order to obtain zero discharge, the gas is captured and fed to a scrubber which separates the CO2 from the other components in the gas. This CO2 vapor is cooled, compressed, and then sent to a dryer/deodorizer. From here the CO2 vapor is condensed and sent to a liquid stripping column where the liquid CO2 can be removed and stored in a tank for further utilization. [1]
Cellulose Dry Weight in Spent Grain (%) Sugar Monomer 16.8 Glucose 100 L.casei Hemicellulose 28.4 Xylose 50 E. casseliflavus 96
Objectives
To identify the major waste streams in the brewing process. To perform mass and energy balances on the brewing process in order to optimize energy usage and determine the total amount of waste produced. (solid, liquid, and gas) To research alternate technologies to either capture, recycle, or reuse these waste materials. Barley Perform an economic analysis. Simplified Brew House Flowchart
Barley
Overall Brewery Capacity Total Beer Production 150,000 hL of beer/year 7,500 L of beer/batch 4 batches/lot 2 lots/day 14 hours/day 5 days/week 1,433.9 kg barley/batch 3 hours/day
360 kg/batch
Roller Mill
Brewing Frequency Hours of Operation Milling
Wet Spent Grains
Ingredients
1.Barley is the largest organic ingredient in the brewing process. The high starch content in barley is converted to simple sugars (e.g. maltose) in the mashing process. 2.Water used in beer production must be sterile and the mineral content must be controlled in order to ensure a consistent flavor. 3.Hops add the bitter component of beer from the alpha and beta acids found in the flowers resins. Beer would be cloyingly sweet without hops. 4.Yeast is a microorganism that metabolizes the converted sugars into alcohol under anaerobic conditions in a process called fermentation. Water
1,400 kg/batch
Milled Malt
Mash
Weight Sugar for Lactic Acid Conversion (g)
2,500 kg/batch
Mash Tun Lauter Tun Sparged wort External Shell and Tube Wort
Bacteria for conversion Lactic Acid Purity (%)
9,800 kg/batch
Solids Stream Wort/Beer Stream
Hops
14.2 kg/batch
Whirlpool Tank Boil Kettle
Brewers spent grain (BSG) is traditionally considered a low-value product that is typically given away to farmers for pennies per kilogram According to Mussatto et al. (2006) cellulosic material can be converted into simple sugars that are >95% pure, which makes these substrates quality sugar sources for bioconversion processes such as lactic acid fermentation Horiuchi et al. (2004) found that L. casei and E. casseliflavus can convert a solution of 100g of glucose and 50 g of xylose into a lactic acid product that is 96% pure.
Anaerobic Digestion of Wastewater
Reactor Type ASBR Control 56,700-62,360 3.0 65 54 248
36,750 kg/batch
Influent Chemical Oxygen Demand (COD) (mg/L) Organic Loading Rate (kg COD/m3day) COD degradation efficiency (%)
56,700-62,360 3.23-8.57 79.6-88.9 78.5-90.5 kg/lot
Clarified 371-418
Yeast
69 wort Chilled wort Fermenter Heat Exchanger / aeration
Volatile Suspended Solids (VSS) removal efficiency (%) Methane Production Yield (L/kg COD inserted)
Equipment Sizing
Height Diamete Equipment (m) r(m) MashTun LauterTun BoilKettle Fermenter 2.0 2.0 3.0 8.5 2.0 3.9 2.0 2.4 H:D ratio 1.0 0.5 1.5 3.5 Headspace TotalVolume (%) (m3) 20 350 20 30 6.4 24.0 9.0 39.0
Energy Requirements
Thermal Energy Required Vessel (MJ) 900 Hot Liquor Tank Mash Tun 260 Boil Kettle 1,900 Amount of Steam Required (kg) 367 106 775
Startup Costs Equipment Costs Material Costs Labor Costs Freight, Insurance and Taxes Overhead Costs Engineering Costs Contractor Fees Auxiliary Costs Total Scale Up Factor Fixed Capital Investment Manufacturing Costs Operating Labor Raw Materials Utilities Total Cost of Manufacturing $ $ $ $ 534,150.00 /yr 2,845,786.59 /yr 168,996.83 /yr 11,837,272.24 /yr $ $ $ $ $ $ $ $ $ $ 1,830,873.60 1,299,920.26 1,158,393.73 238,395.00 810,875.61 469,619.08 111,251.00 300,000.00 6,219,328.27 3.63 22,576,161.62
30,000 L/lot
Brewery Economic Analysis
The economic analysis was performed using the Lang Method which estimates all costs based off of the price of equipment. This model only considers the brewing equipment and does not account for the additional waste treatment technology.
Anaerobic digestion uses microorganisms to break down organic molecules without the presence of oxygen and produces a renewable energy source known as biogas. Biogas contains mostly methane gas which can be combusted to produce thermal and electrical energy in a combined heat and power (CHP) unit. The table above shows that the anaerobic sequencing batch reactor (ASBR) clearly outperforms a conventional fully mixed semi-continuous digestion reactor as a control. [2]
Conclusions
With the implementation of new technologies, zero discharge is a realistic goal that can be achieved. Waste products such as spent grains and waste water can be tre...