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AMIT GANDHI: This is the container.
What happens in this, is biogas gets produced in here.
It goes out the tube through this set of tubing,
and into this container to hold it.
This is just clamped off.
And when you unclamp it, you should
be able to get biogas from this and light it.
This has only been going for a week and a half, or so.
So it may be producing biogas.
If you play with this, you feel some suction on there.
But I don't know how much gas this one produced yet.
I've been keeping it upstairs because upstairs is way
warmer than downstairs in D lab, so, yeah,
when we're done with ours, we're going
to put them upstairs, as well.
The base looks something like this.
So the first thing we have to do is measure out 12 inches
by 7 inches from here.
And each of your groups of three is
going to have to cut one of these out.
So let's start by measuring it.
I'm going to run up and grab a completed one.
[INAUDIBLE] so you guys can see.
Should probably go the other way.
So he gets it.
So you want to measure it 2 inches from here
and 3 to 1/4 inch or
AUDIENCE: 3 and 1/2.
AMIT GANDHI: 3 and 1/2 inches from--
AUDIENCE: OK and then you think [INAUDIBLE]
where's the [INAUDIBLE] Yeah [INTERPOSING VOICES]
REBECCA SMITH: Basically, your only ingredient
in the biogas digester, is this slurry.
So for your container, you'll--
for us, we're going to fill this 3/4 full.
And the ratio of water to human, animal, or vegetable waste
is three parts water to one part [INAUDIBLE]..
And so that is one thing that might make--
basically, that's a factor you'll want to consider.
We were thinking of putting in a biogas digester where
I was in Tanzania, but their water supply
dries up a few months a year, which
meant that just to get water for their family,
they would have to either pay more or walk
a really far distance.
So something like this, would be a lower priority.
And there's a good chance that it
would dry up and stop working.
And after that, it's really hard to get it going again.
So the three things that are really
important for a biogas system are a good supply of manure,
having a hot enough temperature, and having
a good supply of water.
So if you have those three things
it's a really good solution.
But if one is missing, then it will be tricky.
So someone want to dig in.
[LAUGHTER]
Ooh, it's ripe.
AUDIENCE: Oh, OK.
Less terrifying than you should expect.
REBECCA SMITH: Oh, it's nice and dry.
AUDIENCE: OK, so kind.
Are we doing more than one
REBECCA SMITH: Yeah, we're doing [INAUDIBLE]..
AUDIENCE: Cold or hot water?
Lukewarm, oh.
[INTERPOSING VOICES]
AUDIENCE: Is that good enough?
A little more, less?
REBECCA SMITH: No, we only want two quarters full.
So you could do a little tiny bit more.
AUDIENCE: Yeah, stuck to my jeans.
[INAUDIBLE]
[INTERPOSING VOICES]
AUDIENCE: [INAUDIBLE]
Then we need to hot glue the bottle to
Oh, really?
Another, we need another piece like that, right?
That goes.
REBECCA SMITH: [INAUDIBLE] surprisingly well.
AUDIENCE: Yeah.
REBECCA SMITH: I'm pretty impressed with us.
AUDIENCE: Yeah.
So I think this is where the other tubing, the clear tubing,
is supposed to go.
AMIT GANDHI: Yeah.
AUDIENCE: Like through here, right.
AMIT GANDHI: Need to make sure this is sealed first,
for whatever.
REBECCA SMITH: OK, so we need another piece of tubing.
And hot glue down [INAUDIBLE] to the [INAUDIBLE]..
AUDIENCE: I feel like the white [? tape ?] should be smaller.
It should be floating.
I feel like the tube should be less tall because it's
kind of in the way right now.
Yeah.
REBECCA SMITH: So one thing that you can do with the heat
sealer, is make a soda stack.
So this is used for solar disinfection of water.
So it's one way that you can purify water.
What you do, is you can fill any,
basically, clear plastic container with water.
And then you leave it out in the sun for about six hours or so.
And it will kill the bacteria that's in it.
So you might still need to filter it if it's turbid.
But as one step, that's actually pretty effective.
So actually a D-lab alum, MIT alum, called Sean Frayne,
his company is called [? Haddock ?]
and they produce these.
So an alternative would be to just fill maybe a plastic water
bottle, or this is one.
But it uses more material than this so
would be more expensive.
And it's not super easy to fill if you're pouring water
from something.
So what he came up with, is just this bag.
Basically, you can fill the water here.
So it'll just go in
[INTERPOSING VOICES]
REBECCA SMITH: Yeah, so there's a smaller bag here
that has a hole in it.
We actually, in the last session,
spent a while figuring out exactly how
the different parts work because it's a pretty clever design.
And then, so basically, you fold it down
and then the water is sealed in here.
And then after your six hours, you
can just pour it out pretty easily.
So it's a pretty clever design.
And this is something that you can make in the field
to like every time, I think Amy brings a heat sealer
on most of her trips.
Because there are just a lot of useful things
that you can make.
I worked on a pouring dispenser for my D-lab design project.
And we did something kind of like this,
where it's like this, but it's just a one-way valve.
So the idea isn't that you'll be able to get it out afterwards.
But this was a really low-cost way for us
to store the chlorine, and then keep people
from getting it out.
Because we didn't want anyone to be able to siphon it out
or tamper or anything like that.
Another thing you can do.
So this is a drip irrigation kit.
And the way this works, is you would fill it up with water,
and then you'd have a tube coming out.
And from that tube, are many little straws.
And you can direct a small amount of water
straight to your crops.
So it's a much more effective way of irrigating.
And it uses a lot less water.
And someone who I've worked with in Tanzania,
named Bernard, he has actually made
his own heat-sealing machines, like this.
And so he can make the tubes that
would come out of this, just from a heat sealer
and locally available plastic rather than having
to buy that or import it.
Another thing you can do to seal something like this,
if you have male and female pieces like this,
you can take some rubber and make a washer.
And what you do is, have a rubber washer layer
then a plastic or metal washer.
And then you could have your plastic bag.
Basically, this piece is a way to--
and then on the other side, you'd
have another rubber washer, plastic washer.
And then you could have a sealed connection there.
Just as an example of something else you could do.
A way to connect a bag like this to something else.
So the things we have that you can try out.
So this machine and this one work the same way.
It's cool to the touch, but basically,
when you push it down, you'll see a light go on,
and it makes a click.
And then it just melts the plastic.
And you can vary the heat level here.
So in some cases, like for the [INAUDIBLE] bag like this,
you might have some seals where you
want it to go through two bags, but not three,
or something like that.
So you can adjust the level so that it will only
melt through two and leave the other untouched.
And yeah,
AUDIENCE: Are you saying that like
REBECCA SMITH: Yeah.
AUDIENCE: So are you saying that this part?
[INAUDIBLE]
So you can tell the kind of, so this edge of the bag
is this thing.
Yeah
AMIT GANDHI: Yeah.
AUDIENCE: And then with this edge it goes to the little.
To the small, yeah.
And so when I do this then, essentially what happens
is, that I prevent water from coming in from here.
Because when water hits here, this part is stuck there.
So the other side of this tube, is one side of this one bag?
The other side of this?
Yeah, this goes into the bag.