OFFICIAL34 According to the professor, what are two advantages of APS digestion systems? [Click on 2 answers.]

[00:00.00]NARRATOR: Listen to part of a lecture in an environmental engineering class.[00:06.92]MALE PROFESSOR: At the end of yesterday's class, we were discussing landfills and the hundreds of millions of tons of everyday garbage which are deposited into them each year in the United States. [00:18.57]It's a growing problem! Quite simply, we are running out of space to put our garbage. [00:23.80]And this is especially true for solid organic waste: food scraps from home or food processing plants, waste from farms, that sort of thing.
[00:33.41]Did you know that two thirds of the waste sitting in our landfills is organic material? [00:38.79]We have government recycling programs for materials like plastics, glass and metal, yet widespread solutions for organic waste materials haven't really been addressed in the United States. [00:50.38]I think this is just asking for trouble in the future.[00:53.91]So today I want to talk about a technology that offers a potential solution to the problem—anaerobic Phased Solids digestion, or APS digestion.[01:06.11]First of all, what does anaerobic mean? Anyone?
[01:12.88]FEMALE STUDENT: Without oxygen?[01:14.52]MALE PROFESSOR: Correct![01:15.37] APS digestion uses anaerobic bacteria, ones that thrive in the absence of oxygen, to consume, to break down organic material.[01:26.22]MALE STUDENT: Excuse me. Professor. Um...those anaerobic bacteria you are talking about...well, aren't anaerobic bacteria also used in waste water treatment plants?[01:39.05]MALE PROFESSOR: Yes. In fact, they are. [01:40.59]Would you like to explain this to the class?[01:43.28]MALE STUDENT: Sure! So when waste water is treated, one of the byproducts is a thick liquid called sludge. [01:49.60]And aren't anaerobic bacteria used to break down the sludge?[01:53.64]MALE PROFESSOR: That's right.[01:54.49] Anaerobic bacteria have been used in waste water treatment for decades.[01:58.69]MALE STUDENT: So how is this technology different?[02:01.33]MALE PROFESSOR: Good question.[02:02.87] The anaerobic digestion systems used in waste water plants are designed to treat sludge, not solids. [02:10.93]Now, in the past, researchers have attempted to treat solid organic waste with that same equipment. [02:17.01]But there was always a problem. [02:18.99]In order to process the solid waste, the kind we find in landfills, you had to pretreat the solids to turn them into sludge.
[02:27.88]First, by breaking the material apart mechanically into small particles and then adding a lot of water until you got a kind of thick, soupy mix that the equipment could handle. [02:38.68]But that extra step took time and required a lot of energy.[02:43.06]FEMALE STUDENT: That sounds like it would cost a lot.[02:46.59]MALE PROFESSOR: That's right. [02:47.32]But APS digestion is designed specifically to handle solid waste. [02:52.37]So it is much more cost-effective. [02:54.41]The new technology processes organic waste in two phases. [02:58.60]Remember, APS stands for Anaerobic Phased Solids digestion.
[03:03.38]First, the waste material is loaded into a large, closed container, along with different types of anaerobic bacteria. [03:10.81]The bacteria break the solids down into acids and hydrogen gas. [03:15.39]The hydrogen is extracted and the remaining acids are transferred into a different container for the second phase of the process. [03:23.10]There another type of bacteria converts the acids into methane gas.[03:27.97]FEMALE STUDENT: Aren't hydrogen and methane gas bad for the environment though?[03:31.41]MALE PROFESSOR: The answer in this case is no, because they don't escape into the atmosphere. [03:35.95]The gases are captured and can be burned to produce electricity, which saves a lot of money and ultimately decreases our need for fuels like petroleum and coal, which are not only expensive but are also polluting.[03:49.17]MALE STUDENT: So organic waste from landfills could be processed this way?[03:52.71]MALE PROFESSOR: It is certainly one possibility. [03:54.94]And APS digestion systems are very versatile. [03:58.52]They can be installed just about anywhere. [04:00.92]See, anaerobic digestion systems used at waste water treatment plants are huge tanks that hold thousands of gallons of waste water. [04:09.23]But the APS containers are small enough to be set up on site, where the waste is generated, like at food processing plants or on farms.
[04:18.50]So garbage doesn't have to be transported long distances.[04:22.50]As a matter of fact, a couple of universities successfully set up demonstration projects. [04:28.26]They collected food scraps from dining halls and local restaurants and process them in APS facilities. [04:35.38]Not only did the university save money, we are also learning even more about the APS process.[04:41.50]What is the next step forward? [04:43.60]Well, APS digestion uses several different types of anaerobic bacteria, right? [04:49.23]So what are the most efficient bacteria in the process? [04:53.51]If researchers can figure that out, the highest performing bacteria mix for a system could be determined. [5:00.00]Ultimately the goal would be to grow enough of these particular bacteria to support large-scale commercial APS systems.