Sustainability through heat recovery

by Charlotte Atchley
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There are two main reasons bakers decide to pursue sustainability initiatives — the “green” halo and the energy savings reality. Consumers and retail customers continue to be more interested in the behind-the-scenes aspects of food production, and sustainable initiatives give companies a do-good glow.

“I think for a baking company, there are multiple benefits in addition to the overall return-on-investment (ROI),” said Rasma Zvaners, policy director, American Bakers Association (ABA). “It’s a good message for the bakers’ customers as well as the public in general. These days, consumers tend to be a little more interested in or value those products more that may have a story to tell behind them.”

Heat recovery can serve as a piece of a larger sustainability plan and help bakeries save money and increase efficiency. According to US Census Data, in 2010, more than $800 million was spent on purchased fuels and electricity at US commercial bakeries, most of it concentrated in baking and freezing activities. Yes, the baking industry could stand to save in this area.

Bakers can cut energy costs by harnessing the excess heat from ovens and oxidizers and reusing it to power other processes in the bakery. “The technology actually exists in that there is enough heat coming off most of these bakeries that truly can fuel the entire front end of their process: the dough conditioning, manufacturing, makeup,” said Scott Houtz, president, Air Management Technology, Inc. “That entire process can be completely fueled from the energy they’re just wasting, which is major.”

The benefits of this technology are pretty straightforward: saving energy costs and reaping the rewards of a green reputation. Bakers can gain from a reduced carbon footprint and benefit from programs such as the Energy Star program developed by the Department of Energy and the Environmental Protection Agency and through their utility providers.

While going green can cost additional capital investment, bakers see a significant and rapid payback in greenfield facilities. Mile Hi Specialty Foods, Denver, which used the Leadership in Energy & Environmental Design (LEED) program of the US Green Building Council to guide its sustainability programs, installed an Air Management Technology system and saved enough energy to power the equivalent of 525 Colorado homes, according to Paul Chan, former director at Mile Hi and current owner and consultant at GuyChan Global LLC. More than 60% of the facility’s energy came from the recovery system.

Commercial bakers serving on ABA’s Energy & Environmental Committee have seen savings of 60 to 80 million cu ft (Mcf) of gas per day and use the recovered energy to heat water for sanitation, proofers, fermentation rooms and even heat the building. To them, energy recovery is the next large-scale opportunity for bakers, and the opportunities are vaster than many bakers may think.  

Identify opportunities

The oven may be the most obvious place for heat recovery and the proofer the most obvious place to use that excess, but bakers can expand their waste energy sources and uses by just looking around their facilities.

“[Ovens and oxidizers] are two of the biggest areas where you can reclaim heat; however, there are a lot of other opportunities and a lot of new developments,” Mr. Houtz said. Waste energy can come from not only the oven and oxidizer but also thermal waste water, air compressors, refrigeration or carbon dioxide (CO2) transcritical.

CO2 transcritical is one of Air Management Technology’s new developments in energy recovery. Refrigeration using CO2 can generate temperatures of up to 180 or 200°F in the process of cooling the interior of the refrigeration system. With CO2 being a natural source of refrigeration, bakers can use the high-grade heat coming off these refrigeration systems to power other areas of their facilities. 

Many processes around the bakery can benefit from the excess energy. Proofing is the clear choice for using such energy, but bakers also can use it to preheat oven steam feedwater, heat water for sanitation, defrost the freezer and power heat exchangers.

While it may be obvious to use this waste heat for processes relying on heat, it can be used for cooling purposes as well. That extra energy can create ice water, cool mixers, power product coolers and retarders, and dehumidify the bakery. “Not only do we capture the thermal energy for heating, but we can also capture heat to create an absorption refrigeration cycle that will provide all of the cooling to cool ingredient water, mixer jackets — all of that through waste heat,” Mr. Houtz explained.

Looking at the bakery as a whole, instead of just the energy sources and spenders, can help a baker see the opportunities that exist in the facility. “If using LEED, which drives from both a building standpoint and an equipment standpoint, you begin to look at things from a very holistic basis,” Mr. Chan said. “There are other places where bakers can look that will enhance their heat recovery systems, not just coming off an oven or griddle. I challenge every baker to look for those opportunities as well, and once they do that, they’ll see their payback.”

Maximize the potential

By looking beyond preconceived notions of heat recovery and asking the right questions up front, bakers can get the most out of their energy recovery systems.

“It’s important, as the bakery operator, to provide as much information as you can to your supplier,” Mr. Chan said. “As much conversation you can have about short-term and long-term goals for your plant will save you both time and money and get your system right.”

These conversations should cover future plans for expansion: new production lines, changes to the product profile, new equipment and processes. Heat recovery systems can be made flexible to accommodate growing bakeries, but the more that is known upfront, the more that can be prepped for.

Mr. Chan urged that it is also beneficial to be honest about the capital investment the company is willing to put into such a system. Managing expectations about the system’s capabilities as well as costs will ensure the facility’s needs are met and implementation goes smoothly. “Only by having those kinds of conversations with your system providers will you be able to build a system that allows you to meet all your current needs and expand in the future,” he said.

These conversations and planning should help identify the bakery’s energy goals: how much should be recovered and how it can be used. A good place to start is by studying the efficiency of the process without a heat recovery system in place. “If a facility hasn’t done an energy usage study, that would be a good place to identify low-hanging fruit for sustainability programs,” Mr. Houtz said. “Typically, we suggest they do this if a facility hasn’t done one in the past 10 years. There may be new opportunities, or something may be put in place where older technology may no longer be efficient and could be counter-productive to efficient energy use.”

Understanding how the bakery currently uses energy helps the baker and supplier realize the amount of waste heat they can reasonably capture and how much energy is needed to meet the baker’s goals.

By examining their process, bakers can also determine if heat recovery is beneficial to them and how it can fit into a larger sustainability plan. “It has to be thought through with the specifics of the operation itself: the equipment the baker already has, if any additional investments need to be made, what kind of ROI the baker can expect and if it can have an impact on the bottom line,” Ms. Zvaners said. Heat recovery systems are a capital investment and require bakers to weight the costs and benefits of installing one. By evaluating the facility’s waste and energy needs, bakers can ensure they are making sound investments.

“Bakers have to weigh their interest and their financial capabilities to make the capital investment,” Mr. Chan echoed. “Depending on the size of the bakery and what you’re doing, the initial capital can be substantial, but that’s why you talk to your system supplier — they know best in terms of sizing the right systems, how to expand, what should be the initial investment and how to go from there.”

Forging the future path

Talking and planning with a heat recovery system vendor can help a bakery avoid or manage many of the challenges that can come up in installing and implementing this kind of system.

Establishing waste energy output and needs, bakers will know if they can meet their energy requirements with waste energy captured. If the waste is coming up short, balancing can be used to accommodate energy shortfalls. Through balancing, the bakery can generate electricity internally through pumps, cogeneration (creating heat and electricity ) or trigeneration (creating heat, cooling and energy) to make up the difference. “Essentially you’re taking waste energy and balancing that from these sources to create net zero,” Mr. Houtz explained. 

Converting old utilities is another common challenge with energy recovery systems, but one that is manageable. While steam has been the mainstay for heating bakeries, energy recovery systems work best with fluids, so bakeries have to convert to hot water. “Those can sometimes be a little bit of a challenge, but it’s something we’ve ‘been there, done that,’ ” Mr. Houtz said.

The highest hurdle when it comes to heat recovery, however, is ROI. While there is definitely a halo benefit to going green for any bakery — with certain customers and end consumers — it’s the measurable ROI that really talks and wins bakers over. “Sustainability and green are great, but a lot of people don’t want to invest money in sustainability unless they can see an ROI, and understandably, everyone is looking to make a profit,” Mr. Houtz said.

In a greenfield plant, he said, this is easy to do. The production lines can be designed from the ground-up with sustainability initiatives in mind. Equipment can be purchased and utilities put in place that are conducive to heat recovery. An existing plant, however, is another story entirely. Equipment and utilities in place for years or equipment just purchased may not be ideal for energy recovery systems. And while the price of natural gas may be volatile, when prices are low, ROI in an existing facility isn’t as immediate as it is in a brand new plant.

Bakers that are interested in heat recovery in existing facilities can still benefit, however. It’s just a more long-term investment to make. “It provides a pathway to replacing individual systems to eventually achieve that goal of being sustainable through a heat recovery system,” Mr. Houtz said — a pathway to sustainability, he called it. By installing a heat recovery system, a baker creates an opportunity to put sustainability at the forefront of the company culture. As older equipment must be replaced, bakers can invest in equipment that will be compatible with heat recovery and, over time, create a facility that is more energy-efficient.

This level of investment demands a company commitment to sustainability when it comes to short-term and long-term results. “ROI, when you look at any energy saving scenario, is going to be the biggest challenge,” Ms. Zvaners said. “There needs to be a conscious effort for people to say, ‘This is something we’re going to focus on, and we’re going to make it happen,’ but again, it comes down to, ‘Do we have the time, energy and the resources to make a good investment so we can see something coming back from that in the short term?’ ”

While short-term ROI is definitely a plus, and bakers can see immediate returns in a greenfield facility, heat recovery is not an exclusively short-term solution to a bakery’s energy needs, as Mr. Houtz explained. To look at it only in terms of immediate ROI would do energy recovery a disservice. “Heat recovery is a lifetime plan, so once you do it, it will be there for life,” he said.
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